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Famous mineral localifies: Llallagua, Bolivia.

Llallagua, once one of the world's richest tin deposits, is one of the most important mineral localities in South America. It is the type locality for five mineral species (vauxite, metavauxite, paravauxite, sigloite and jeanbandyite) and has also produced some of the world's best specimens of stannite, cylindrite, monazite, bismoclite, and other species. The mine is still in operation and specimens continue to be found in the upper levels.

INTRODUCTION

Llallagua is a tin deposit located at an altitude of more than 4, 000 meters (13, 000 feet) in the eastern Andes Mountains in Bustillo Province, northern Potosi department, Bolivia. It is located about 75 km south-southeast of the town of Oruro and about 270 km south-southeast of La Paz. In the middle of the 20th century Llallagua was the most famous and productive tin mine in the world; it is now past its peak, but mining is still active, and new specimens often reach the collector market in North America and Europe.

Llallagua specimens may appear in collections under several loosely interchangeable locality names, including "Llallagua, " "Siglo Veinte, " "Siglo XX, " and "Catavi"--all of these names refer to the same locality! Llallagua (pronounced "yah-YAH-wa"), the term most commonly seen on specimen labels, refers to the city in which the mine is located. Llallagua (according to Gordon, 1944) is the Quechua Indian word for "mammae" or "twin peaks." Catavi was both the name of the nearby mill and the name of the administrative division of COMIBOL (the State mining corporation) which controlled the mine during the years when it belonged to the State. Siglo Veinte, or Siglo XX (= "Twentieth Century" in Spanish) is the actual name of the mine, commemmorating the fact that it was opened at the beginning of the 20th century. Other terms that may appear on labels, especially in local Bolivian collections, are "Salvadora, " for the mountain which hosts the orebody, or the names of individual Secciones (Sections)--miner-owned cooperatives on different parts of the mountain--including "Cancaniri, " "Dolores" and "Dolores Atras." Further compounding confusion for foreigners, Bolivian collectors often write only the name of an adit or vein on their labels, omitting the mine name; for example, an old monazite specimen in the San Diego Natural History Museum, labeled simply "San Jose" is from the San Jose vein at Llallagua, not the famous San Jose silver mine in Oruro city.

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HISTORY

Llallagua is much richer in tin and poorer in silver than the similar subvolcanic deposits of Potosi and Oruro (Hyrsl and Petrov, 1996). Nevertheless, silver was mined in Llallagua in the early 19th century (Bandy, 1944), although it is not known what the silver ore minerals were, and reports of native silver can no longer be substantiated. Since minerals containing essential silver are present only as insignificant traces (e.g. andorite), the silver ore minerals may have been franckeite and stannite (both of which commonly bear a few tenths of a percent silver), and sphalerite with micro-inclusions of tetrahedrite. In the late 1990's, a galena vein with minor pyrargyrite was worked in neighboring Uncia, on the southeast side of the mountain, and it is possible that such veins were found extensively during the early 19th century but have been obliterated by mining. In any case, the earliest published reference to minerals from the mine appears to be a note by Arzruni (1884) describing cassiterite crystals that had been obtained in Llallagua. The earliest account of the mine itself is Stelzner (1897).

The modern history of Llallagua begins with prospecting for tin at the end of the 19th century and soon thereafter becomes entangled with the career of Simon Iturbi Patino, one of the most remarkable men in Bolivian history. Patino was a mestizo born into humble circumstances in 1868 in the village of Santibanez outside Cochabamba city. According to a wide-spread story, he was working as an assistant in a rural general store in Cochabamba when, around 1900, he made a modest personal loan to a tin miner and received in return the deed to a small tin mine called Juan del Valle, on the southeast side of Mt. Salvadora in Llallagua. He moved there in 1903, did some digging with his wife, and soon found a cassiterite vein which turned out to be fabulously rich. He opened his first mine on the southeastern side of the mountain while a Chilean company, "Compania Minera de Llallagua, " was operating a mine on the northwest side. Already by 1905 Patino's company had become one of the most important in Bolivia, and was beginning to buy up all of the other properties in Llallagua. By 1924, when he finally bought out the Chileans, forming "Patino Mines & Enterprises Consolidated, " he was well on his way to becoming one of the wealthiest men in the world.

Little by little Patino acquired other important Bolivian mines (e.g. the Huanuni tin mine and Kami tungsten mine), as well as tin mines in Malaysia and even tin refineries in Europe. Along with Moritz (Mauricio) Hochschild and Franz Aramayo, he became one of the three so-called Bolivian "tin barons" who in some ways were more powerful than the State itself. In the decades before the mines' nationalization in 1952, the mining conglomerates run by these three men accounted for approximately 70% of all Bolivian mineral exports by value. Under the leadership of "the barons, " tin mining reached its historic peak in 1929, when Bolivia produced 49, 191 metric tons of the metal.

It is fortunate for the scientific record that, over the years, three very competent mineralogists have been able to study the Llallagua minerals on site and have published their observations. The first was the American mineralogist Samuel Gordon (1897-1953) (see Montgomery, 1973-1975), who visited the mines on behalf of the Philadelphia Academy of Natural Sciences in 1921, 1925 and 1929 specifically to study the mineralogy and collect specimens for the Academy. He visited over 100 working stopes, as well as examining remaining pillars of ore in abandoned but still accessible stopes. He personally collected a great many specimens, and was given more by miners and engineers. These he brought back with him to Philadelphia where he carried out detailed analyses, especially including goniometry which yielded many crystal drawings. His trips were described in the Annual Reports and Yearbooks of the Academy in 1922, 1926 and 1930, and he published all of his mineralogical findings in his monograph Mineralogy of the Tin Mines of Cerro de Llallagua, Bolivia in the Academy Proceedings in 1944.

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The second mineralogist of note at Llallagua was Friedrich Ahlfeld (1892-1982), "the Father of Bolivian geology, " who served in Bolivia as Chief Geologist for the Bolivia Government in 1935-1936 and 1938-1946, and worked for Patino Mines and Enterprises (operators of the Llallagua mine) from 1951 to 1952. He published numerous works that dealt in part with the mineralogy of Llallagua, most prominently his 1937 book with Jorge Munos-Reyes, Los Minerales de Bolivia (now in its sixth edition) and his 1941 and 1954 books on the mineral deposits of Bolivia.

The third important investigator was the American mineralogist and mining engineer Mark Chance Bandy (1900-1963), who worked for the Patino company from 1936 to 1947. Much of that time he spent working at Llallagua, where he progressed from Chief Geologist to Chief Engineer to General Manager, all the while making careful records of the many mineral occurrences encountered in the course of mining, and amassing a superb personal collection of Llallagua minerals (later donated to the Natural History Museum of Los Angeles County; see Jones, 1973). Bandy published the results of his work in his 1944 monograph, Mineralogy of Llallagua, Bolivia. The works of these three authors form the basis of the current review, augmented by information on more recent finds known to the current authors.

By the end of the 1930's, Patino's companies controlled more than 60% of the world's tin business. But Patino himself had moved to Europe in 1912, and ran his empire from there, seldom returning to Bolivia. (His children intermarried with European nobility, and his descendents presently live in Switzerland and France.) Simon Patino died in Buenos Aires in 1947, and his tin empire passed into his children's hands--but only for the next five years.

Block-caving was introduced in 1950 and Siglo XX became the largest, most productive and most modern tin mine in the world. But many Bolivians resented the fact that the wealth generated by Bolivia's tin was being frittered away in Europe, and rebellious sentiments simmered. In 1952 came revolution and nationalization, and the Patino family lost all of its Bolivian mines (although the overseas portions of its empire lasted much longer). The Siglo XX mine fell under the control of the State mining corporation, COMIBOL (Corporacion Minera de Bolivia).

The first few years after the revolution were trying times for the mine engineers, laboratory workers and other technical staff, because the miners' unions enjoyed enormous political power despite their members' lack of education and technical expertise. Administrative and technical departments were forced to take miners onto their staffs (reportedly with disastrous effects on laboratory glassware). Strikes and violence were frequent, with many miners supporting the Communist party. Llallaguans tell stories about politically active miners hiding underground for weeks at a time in remote galleries when the police or army came looking for them, their wives smuggling food down to them by way of forgotten adits and stopes.

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In the 1960's another problem arose: theft of ore by organized bands of hundreds of jucos (from the Quechua word for "nocturnal raptor"). The jucos were unemployed miners who created fictitious mining claims on other mountains but in reality were sneaking into the Siglo XX mine to highgrade cassiterite and sell it to Llallagua's COMIBOL-owned Catavi mill. The ex-miners were soon joined in this juqueo by thousands of indigenous campesinos, increasing the headache for COMIBOL. Cornelius Bloot, the Dutch general manager at Catavi, knew very well what was going on, but he bought the jucos' concentrates anyway, partly out of compassion and partly out of pragmatism: he knew that the jucos would just sell the concentrates to another mill if Catavi refused to buy them. Eventually COMIBOL resigned itself to turning a blind eye to juqueo, which provided concentrates to the mill more cheaply than COMIBOL itself could--and there was no need to provide medical or other benefits to the poor jucos!

The great days of commercial mining at Llallagua were ending in any case. The world price of tin had been falling since the end of World War II, the politicians sucked up any profits from tin exports without leaving much for COMIBOL to reinvest, and COMIBOL was awash in red ink. So COMIBOL finally left Llallagua in the mid-1980's and handed the mines over to the local miners. By this time the mountain was honeycombed with more than 800 kilometers of galleries.

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At present, about 5, 000 miners still work at Llallagua, but conditions are much deteriorated from the modernity of the 1950's and 1960's. The mountain is owned by five cooperatives of mostly indigenous miners, working with no capital and little technical support; these miners earn as little as $60 per month. Trains, hoists and crushers no longer work. Miners carry ore out in rucksacks, crush it by hand with curved steel rockers, and concentrate it themselves with buddles. If Georgius Agricola were to visit Llallagua today, he would feel right at home!

The total amount of tin produced by the Siglo XX mine is unknown, but it had already yielded about 500, 000 tons by the early 1960's (Ahlfeld and Schneider-Scherbina, 1964). At various times the mine also produced lesser quantities of silver, tungsten (mostly during World War I) and bismuth (mostly in 1923-1925).

GEOLOGY

Cerro Salvadora, the mountain in which the Llallagua tin deposit is located, is a conical subvolcanic stock of Tertiary age, similar to the stock deposits of Potosi and Oruro. The Llallagua deposit crops out as a 1.1 x 1.7-km ellipse on the surface; narrowing with depth, it measures 1 km x 700 meters at a depth of 650 meters below the peak of Cerro Salvadora. It is made up of porphyry and porphyry breccia, having probably originated as an explosive vent. Llallagua's stock, also like Potosi and Oruro, is heavily altered, and almost all of the original feldspar in the volcanic rock has disappeared, having been replaced by quartz, sericitic muscovite, clay, tourmaline, pyrite and other minerals. However, tourmalinization played a much bigger role at Llallagua than at Oruro or Potosi: Llallagua may represent the world's largest deposit of tourmaline (although the tourmaline found there is mostly microfibrous, and there is no gemmy material). The intrusion was sericitized, tourmalinized and silicified before any of the ores were deposited. The prior silicification of the wall rocks prevented the ore-forming solutions from penetrating and replacing the porphyry, so the bulk of the ore was deposited in open shear zones and fissures.

Forty-seven main veins and approximately 1500 small but rich veins are known in the deposit, most of them trending northeast-southwest. Most of the tin ore was produced from veins transecting the volcanic stock, although some of the veins (e.g. the Contacto, Plata, Bismarck, and San Fermin) extend into the surrounding sedimentary rock, and the Carnevalito lies entirely in the sediments. The Contacto vein, perhaps the most important for mineral collectors, got its name from the fact that it crosses the contact between the igneous intrusion and sedimentary country rock.

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Llallagua is a classic example of a "telescoped" deposit, in which high-temperature minerals (especially cassiterite and pyrrhotite) have been deposited in a low pressure, near-surface (xenothermal) environment. Low-temperature (kryptothermal) sulfides were later superimposed in the same veins, resulting in the characteristic complexity of Llallagua mineralization.

The principal access tunnel, Siglo XX, situated at the border of the town, runs along Level 650 beneath Cerro Salvadora; the richest mineralization was found below this level. (Levels in Siglo XX are customarily designated by the number of meters below the peak of Cerro Salvadora.)

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The first depositional stage of the veins is represented by quartz, tourmaline, bismuthinite and cassiterite, with minor wolframite and fluorapatite. Some of the veins were fabulously rich. Turneaure (1960) mentioned that the San Jose/San Fermin ore shoot, which had a maximum stope length of 700 meters, with ore extending for 600 meters vertically, in many parts contained 25% or more of tin. In the second stage, pyrrhotite and franckeite were deposited, and in the next stage almost all pyrrhotite was replaced by pyrite, marcasite and siderite.

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The various phosphates much beloved by collectors, most abundantly wavellite, were formed in the final stages of hydrothermal deposition, and were derived mostly from decomposition of primary fluorapatite. Greenockite and allophane were also deposited in this stage.

MINERALS

Allophane [Al.sub.2]Si[O.sub.5]-----[H.sub.2]O

Pearly white to capucine-orange mammillary masses of resinous, amorphous allophane form the matrix in some vauxite, vivianite and wavellite specimens. The allophane is unstable; unless kept under water it dehydrates to a chalky aggregate that gradually crumbles away, leaving thin crusts of blue vauxite with empty mammillary impressions on the bottom. More such specimens were found in 2001. A phosphate-rich variety containing about 8% [P.sub.2][O.sub.5] was described by Gordon (1944) as the mineral "phosphate allophane, " but was discredited two years later as allophane. It also forms masses mixed with marcasite, pyrite and sphalerite.

Bandy (1944) noted that, although all transparent, pale, soft, opaline material found in the mine is placed under this heading, some is undoubtedly halloysite and some may be opal.

Alunite K[Al.sub.3](S[O.sub.4])[.sub.2](OH)[.sub.6]

Gordon (1944) found rare white porcelaneous masses of alunite.

Andorite PbAg[Sb.sub.3][S.sub.6]

Gordon (1944) described andorite in small, brilliantly metallic, striated, prismatic steel-gray crystals to 1 mm, all covered by wavellite, with stannite and pyrite on quartz. Gordon identified 38 different crystal forms including five new ones. Andorite is quite rare in Llallagua, occurring only as small crystals in no way comparable to the much better crystals from Oruro, but it remains the only confirmed silver mineral in the central part of the Llallagua deposit.

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Anglesite PbS[O.sub.4]

Bandy (1944) mentions a small vein composed of anglesite and quartz, 4 km northeast of the stock.

Antlerite [Cu.sub.3](S[O.sub.4])(OH)[.sub.4]

Green acicular crystals of antlerite coating quartz were found on upper levels of the Salvadora vein (Bandy, 1944).

Arsenic As

On the Level 411 of the Demasias vein, a strange mass that looked like dark limonite was found to consist of alternating lamellae of native arsenic, realgar and gypsum (Davy, 1920). It appears to have formed through the oxidation of arsenopyrite.

Arsenopyrite FeAsS

Arsenopyrite has been found commonly in several veins, as well-formed twinned crystals, as sheaf-like groups of crystals up to 2 cm long, and as vuggy masses over a meter thick. It is widely distributed throughout the deposit, and is abundant in the Polvorin and Plata veins on the upper levels, although its presence tends to indicate low tin values. Fine specimens were found in the early 1940's on Level 275, and sheaf-like crystal clusters have been found along the Contacto vein on Level 355. "Magnificent specimens" of rounded and sheaf-like groups were found in 1941 in the Salvadora vein, above Level 215, and smaller crystals were collected along the San Jose vein below level 650 (Bandy, 1944). A vug in the footwall of the Contacto vein, on Level 250, yielded brilliant crystals of arsenopyrite, wolframite, jamesonite and bismuthinite perched on spongy quartz.

Augelite [Al.sub.2](P[O.sub.4])(OH)[.sub.3]

Augelite was found by Bandy (1944) as small tabular crystals in the Bismarck vein.

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Azurite [Cu.sub.3](C[O.sub.3])[.sub.2](OH)[.sub.2]

Gordon (1944) found tiny azurite crystals with malachite and covellite on weathered chalcopyrite.

Barite BaS[O.sub.4]

Tabular barite crystals are associated with a recent hot spring deposit of tungsten-bearing psilomelane and opal at Uncia.

Bismite [Bi.sub.2][O.sub.3]

Several products of the oxidation of bismuthinite have been found as earthy aggregates. Bandy (1944) lumps them together under bismite, but they need further study.

Bismoclite BiOCl

Bandy (1944) described pseudomorphs of massive micaceous bismoclite after bismuthinite with nice colorless crystals (!) of bismoclite to 2 mm in vugs. These came from below Level 411 of the Carnevalito vein.

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Bismuth Bi

Native bismuth, younger than bismuthinite and ferberite, was occasionally found in the deeper levels. Ahlfeld and Munos Reyes (1955) mention scarce granular masses from Level 650 at the extreme northern end of the San Jose vein, where it was associated with bismuthinite, filling spaces between quartz crystals. The biggest cleavable bismuth masses found measured 10 cm across. Greene (1943) described pinkish native bismuth in association with cassiterite, bismuthinite, wolframite and quartz. An interesting lot of specimens came in the early 1990's from about Level 450 of the San Jose vein, where small masses of native bismuth associated with blue spherules of variscite were found.

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Bismuthinite [Bi.sub.2][S.sub.3]

Bismuthinite is one of the earliest formed minerals in the veins, and some of the largest known crystals of this species from anywhere in the world have been found at Llallagua. It forms lathshaped crystals to 1 x 30 cm (Gordon, 1944) in vugs filled with iron sulfides or cassiterite, fluorapatite and wolframite. Freestanding terminated bismuthinite crystals to 1.6 cm can still be found rarely on the dumps. Massive bismuthinite, together with wolframite, is still produced in small amounts on the lower levels of the San Jose vein; there was significant commercial production from this vein between 1923 and 1925.

Bismutite [Bi.sub.2](C[O.sub.3])[O.sub.2]

Bismutite has been reported from Llallagua by Petrov et al. (2001), on the basis of information on specimen labels.

Bornite [Cu.sub.5]Fe[S.sub.4]

Bornite occurs as thin films on pyrite, as an alteration product of stannite (Ahlfeld and Munos Reyes, 1955).

Boulangerite [Pb.sub.5][Sb.sub.4][S.sub.11]

Gordon (1944) measured a prismatic crystal from the Contacto vein that he concluded was boulangerite.

Bournonite PbCuSb[S.sub.3]

Bandy (1944) mentioned small gray grains of bournonite.

Brochantite [Cu.sub.4.sup.2+](S[O.sub.4])(OH)[.sub.6]

Brochantite has been reported from Llallagua by Petrov et al. (2001), on the basis of information on specimen labels.

Caledonite [Pb.sub.5][Cu.sub.2](C[O.sub.3])(S[O.sub.4])[.sub.3](OH)[.sub.6]

Bandy (1944) described crusts of caledonite and linarite near Level 355 of the Salvadora shaft.

Cassiterite Sn[O.sub.2]

Cassiterite is by far the most important ore mineral in Llallagua, commonly forming huge masses containing crystal-lined vugs. As of 1944, ore sufficient to yield more than 350, 000 tons of tin had been produced. Ore shoots containing 40% to 50% cassiterite and measuring 2 meters across and 30 meters in length were mined on the San Jose/San Firmin vein, and blocks of nearly pure cassiterite 2 meters across have been recovered (Gordon, 1944).

Although cassiterite specimens from Llallagua never attain the size and beauty of the best specimens from the Viloco mine in La Paz department, they can be quite attractive. The most common type of Llallagua cassiterite specimens shows black twinned crystals to 1 cm, in most cases on quartz but also on tourmaline, pyrite or monazite. Cassiterite is frequently found coated with drusy wavellite.

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Bandy (1944) classified Llallagua cassiterite habits into three of the types established by Ahlfeld (1955): Types II, III and V. Type II is represented by the black to dark brown, color-zoned crystals and massive ore that are the most common. The largest crystals, with faces up to 1 cm, are from the Salvadora vein, and somewhat smaller crystals have come from the San Jose/San Firmin veins. Type II crystals are contact-twinned on (011) (the Zinnwald Law), and repeated twinning commonly results in cyclic twins. The faces tend to be irregular and striated.

The rare Type III crystals, simple combinations of prism and dipyramid, are small and unzoned; they range from colorless to pale yellow and brown. Doubly terminated crystals are common, but the size rarely exceeds 3 mm. Good specimens have come from the upper portions of the Contacto vein, especially on Level 295 (associated with stannite) and along the rim of the Animas Branch M above Level 250. Some clusters show a marked tendency toward parallel growth, and often coat breccia fragments in fault zones (Gordon, 1944). Attractive honey-yellow crystals were found in the Inca vein above Level 180.

Type V cassiterite is cryptocrystalline with a colloidal texture, botryoidal form and radially fibrous structure--what is comonly referred to as "wood tin." Good specimens have been found in the Contacto vein above Level 250, and along a branch of the Salvadora vein near Level 180. Greene (1943) mentions rare cassiterite stalactites to 4 cm long.

Most attributions of "wood tin" specimens to Llallagua are erroneous; this material is found much more abundantly on a volcanic plateau in the Macha area, about 80 km southeast of Llallagua.

On the vast dumps of volcanic waste in Llallagua it is still easy to find vugs with tiny translucent dark brown cassiterite crystals associated with quartz and tourmaline.

Cervantite [alpha]-[Sb.sup.3+][Sb.sup.5+][O.sub.4]

Several products of the oxidation of stibnite and jamesonite have been found as earthy aggregates. Bandy (1944) mentions them together under cervantite, but the specimens will require further study for accurate characterization.

Chalcanthite CuS[O.sub.4]-----7[H.sub.2]O

Masses of beautiful blue crystals of post-mining chalcanthite are found in several sections of the mine, especially along the San Jose vein, growing in fissures in the rock walls or hanging from wooden beams, and these are popular with local mineral collectors, although many of their specimens of calcantita are really the more common cuprian melanterite.

Chalcocite [Cu.sub.2]S

Chalcocite has been described as an alteration product of stannite (Ahlfeld and Munos Reyes, 1955). It is more abundant in the southern part of the mine.

Chalcopyrite CuFe[S.sub.2]

Chalcopyrite occurs very rarely with supergene Cu sulfides, and as microscopic inclusions in sphalerite.

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Chalcosiderite Cu[Fe.sub.6](P[O.sub.4])[.sub.4](OH)[.sub.8]-----4[H.sub.2]O

Blue spheres of chalcosiderite up to 2 mm in diameter occur in quartz cavities, accompanied by small vivianite crystals.

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Childrenite FeAl(P[O.sub.4])(OH)[.sub.2]-----[H.sub.2]O

Childrenite has been found as druses of pale brown to dark brown, millimeter-size tabular crystals in parallel growth coating fissure surfaces to a half-meter square (Bandy, 1944), and as rosettes of translucent, yellow-orange to zinc-orange tabular crystals encrusting paravauxite (Gordon, 1944). The crystal size is typically up to about 1 mm, though rare crystals to 3 mm have been collected. Bandy (1944) reports it from the Contacto vein, the southern end of a branch of the Serrano vein, and on the San Jose vein from Level 355 to Level 516. Although it is often found in relative abundance without associated species, it is usually found coating paravauxite or wavellite. Loose aggregates of childrenite filling vugs have been found in the hanging wall of the Contacto vein (Bandy, 1944).

More recently childrenite has been found as very dark brown, radiating spheres up to about 3 mm in diameter, many with whitish centers; some of the spheres perch on vivianite. The authors' chemical analysis showed Fe strongly prevailing over Mn, in both the brown and white portions, suggesting that there is no eosphorite at Llallagua. Local Bolivian dealers are selling specimens of this material erroneously labeled "sigloita, " and the misidentification has been uncritically perpetuated by some foreign dealers; caveat emptor!

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Chrysocolla (Cu, Al)[.sub.2][H.sub.2][Si.sub.2][O.sub.5](OH)[.sub.4]-----n[H.sub.2]O

Chrysocolla occurs sporadically as a decomposition product, perhaps of post-mining origin. Pale blue crusts can be seen in the vertical north wall of one of the collapse craters caused by block caving.

Cookeite Li[Al.sub.4]([Si.sub.3]Al)[O.sub.10](OH)[.sub.8]

Very surprising was a single find of cookeite as pearly cream-colored scales in milky quartz, together with bismuthinite needles (Gordon, 1944).

Copper Cu

Native copper has been found in several places just below the oxidation zone in stannite-bearing veins, very rarely as tiny crystals to 1 mm.

Cordierite [Mg.sub.2][Al.sub.4][Si.sub.5][O.sub.18]

Bandy (1944) found perfect, simple prismatic crystals of cordierite, largely altered to gray masses of pinita, reaching 2 cm long and 1 cm thick, in quartz porphyry dikes cutting the breccia in the volcanic stock. The cordierite probably originated by assimilation of slates into the magma. Grains of blue to violet, unaltered cordierite occur in the country rock tuff near Catavi.

Covellite CuS

Covellite is seen commonly as thin films with chalcocite, both species having weathered from stannite.

Crandallite Ca[Al.sub.3](P[O.sub.4])[.sub.2](OH, [H.sub.2]O)[.sub.6]

Crandallite is common in a mixture with variscite as part of agate-like phosphate concretions. Brownish pink botryoidal micro-aggregates are also seen on some recent vauxite specimens.

Creedite [Ca.sub.3][Al.sub.2](S[O.sub.4])(F, OH)[.sub.10]-----2[H.sub.2]O

Creedite has been reported from Llallagua by Petrov et al. (2001), on the basis of information on specimen labels. However, the authors believe that the specimens in question are probably mislabeled as to locality, and confirmation of the source is lacking. Therefore the occurrence at Llallagua must be considered doubtful.

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Cronstedtite [Fe.sub.2.sup.2+][Fe.sup.3+](Si, [Fe.sup.3+])[O.sub.5](OH)[.sub.4]

Black crystals of cronstedtite with triangular cross-section, displaying only {20[bar.2]1} and {0001} faces, as well as compact masses of cronstedtite, were once found on hisingerite, marcasite, pyrite, siderite and rhodochrosite. According to Bandy (1944), the best crystals came from Level 411 and Level 516 of the Contacto vein. Also, cronstedtite is abundantly present on recent vivianite specimens, as olive-green mammillary crusts associated with pyrite and sphalerite.

Cuprite [Cu.sub.2]O

Small masses of cuprite have been found with native copper in the Inca and San Jose veins.

Cylindrite (Pb, Sn)[.sub.8][Sb.sub.4][Fe.sub.2][Sn.sub.5][S.sub.27]

Cylindrite occurs in a unique habit consisting of very thin, leadgray folia rolled up into cylinders. Its occurrence is limited to deposits between Oruro and Chorolque in Bolivia; specimens from the type locality of Poopo are better known, but the occurrence at Llallagua is unusual in that, instead of being solidly intergrown in masses, the cylinders (up to 1 cm long) have grown free, projecting into vugs and having one "termination" exposed. Cylindrite crystals like these, always accompanied by franckeite, are still occasionally found in recently produced, vuggy franckeite ore. The best known cylindrite specimen from Llallagua, showing cylindrite crystals on stannite, is in the Bandy Collection, Natural History Museum of Los Angeles County.

Diadochite [Fe.sub.2](P[O.sub.4])(S[O.sub.4])(OH)-----6[H.sub.2]O

Vitreous stalactitic masses of diadochite of colloidal origin were once found on Level 320 of the Contacto vein, and large masses have been found in other stoped-out tin veins. Bandy (1944) reported that coffee-brown diadochite formed in great abundance on the floors of old workings below Level 650, and formed layers to 60 cm deep in parts of Level 720 after it had been flooded for over ten years. Some diadochite masses were plastic when first found, but dehydrated rapidly outside the mine, crumbling into pieces smaller than 1 cm.

Epsomite MgS[O.sub.4]-----7[H.sub.2]O

White epsomite fibers occur on melanterite and chalcanthite stalactites.

Evansite [Al.sub.3](P[O.sub.4])(OH)[.sub.6]-----8[H.sub.2]O

Pale orange, transparent, resinous masses of evansite, much resembling tree resin, are occasionally found in association with metavauxite.

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Faustite (Zn, [Cu.sup.2+])[Al.sub.6](P[O.sub.4])[.sub.4](OH)[.sub.8]-----4[H.sub.2]O

Faustite is known on a single specimen from the Siglo XX mine in the collection of the A. E. Seaman Mineral Museum, Michigan Technological University (G. Robinson, personal communication, 2005). The specimen, which was collected in the early 1940's by Reynolds M. Denning, consists of a 3-cm marcasite pseudomorph after pyrrhotite intergrown with quartz, the surface of which is encrusted with microcrystals of colorless wavellite, pinkish sphalerite, orange greenockite and sparse, porcelaneous, white spheres of faustite. Identification of the faustite was made by X-ray diffraction and confirmed by energy dispersion X-ray spectroscopy, which showed minor concentrations of Fe and Cd in addition to the major elements Zn, Cu, Al and P.

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Feldspar Group

Unaltered crystals of orthoclase and plagioclase (probably oligoclase), including Carlsbad-law twins, have been found rarely as phenocrysts in the volcanic porphyry. Almost all Carlsbad-twinned crystals of feldspar (both orthoclase and plagioclase) have been replaced by mixtures of younger minerals, e.g. tourmaline, sericite (= fine-grained muscovite), quartz, kaolinite, and rarely cassiterite or pyrite (Hyrsl and Petrov, 1998). These pseudomorphs can reach up to about 8 cm.

Ferberite (Fe, Mn)W[O.sub.4]

"Wolframite" (mostly ferberite) was once an important Llallagua ore mineral, commercially produced as tungsten ore during World War I, but good crystals are much less common than from other Bolivian mines such as Tazna.

Ferberite occurs at Llallagua in opaque to translucent, black to reddish brown crystals up to 5 cm or more, showing the characteristic perfect cleavage parallel to (010). The crystals are usually tabular on (100), but may also be elongated parallel to [100]. Microcrystals, on the other hand, tend to be prismatic/bladed and elongated parallel to [001]. Twinning is common, usually about [001], and "fish-tail" to triangular twins are also known, from the San Jose, San Fermin, Salvadora, Paralela and Blanca veins. Fine tabular crystals have also been found in quartz-lined vugs in the Salvadora, Bismarck, Contacto and San Miguel veins (Bandy, 1944). The larger crystals occur on cassiterite and bismuthinite, and are sometimes found in columnar aggregates. Small, black acicular crystals in radial aggregates have been found on quartz crystals with secondary bismuthinite crystals (Gordon, 1944).

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Florencite-(Ce) Ce[Al.sub.3](P[O.sub.4])[.sub.2](OH, [H.sub.2]O)[.sub.6]

Creamy white florencite-(Ce) crystals up to 1 cm were found a few years ago, together with pyrite and color-changing monazite-(Ce), in the Dolores Section gallery.

Fluorapatite [Ca.sub.5](P[O.sub.4])[.sub.3]F

Fluorapatite, one of the most beautiful Llallagua minerals, used to be quite abundant as colorless to purple or pink, translucent to transparent, tabular to prismatic crystals, although fine specimens are almost unobtainable now. It was the principal gangue mineral in some of the richest cassiterite veins mined in the 1920's, and is considered to be the precursor from which the extensive suite of other phosphates (vauxite, paravauxite, metavauxite, wavellite, variscite, crandallite, childrenite, vivianite and allophane) developed, except for monazite and xenotime. Bandy (1944) observed that fluorapatite is mostly confined to veins in the sedimentary rocks and the igneous rocks near the sedimentary contacts.

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Fluorapatite crystals to several centimeters have been found emplanted on quartz and ferberite crystals in many vugs in various veins. The most prolific source of fine fluorapatite specimens has been the Contacto vein, especially the area above Level 295, where large, colorless, transparent to translucent crystals to 5 cm were found in vugs. The crystals, showing a habit composed of nine different forms, range in proportion from equant to thin tabular. Most fluorapatite is covered by a crust of wavellite which can be flaked off. Tabular crystals from the Animas vein (Level 235) show color zoning, from colorless in the core to pink to purple in the outermost zone. In the 1930's large, fine pink fluorapatite crystals were found along the Bismarck vein (above Level 383). In the early 1940's small crystals were found abundantly on Levels 411 and 446. Some crystals are preferentially frosted on the faces of certain forms and lustrous on others (Bandy, 1944). Fluorapatite crystals from the Contacto vein (on Level 250 and above Level 295) commonly are on stannite matrix and have associated jeanbandyite. Crystals filled by fine jamesonite needles have also been found. Along the San Jose/San Firmin vein (Levels 516 to 481), flat tabular crystals altered to a white clay-like mineral are found embedded in cassiterite.

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Llallagua fluorapatite has a very strong form-dependant fluorescence under ultraviolet light, yellow-orange on {10[bar.1]0} faces and bright violet on {0001} faces. This fluorescence was studied in detail by John Rakovan (2003), who also determined the age of the fluorapatite crystallization at about 43.8 Ma (million years). The crystals also exhibit an alexandrite-like effect: they are pale pink in daylight and tungsten light but lemon-yellow under fluorescent lighting, a phenomenon which indicates a high content of certain rare-earth elements.

The latest discovery, in 2002, yielded tabular fluorapatite crystals to 3 cm wide, but only about 4 mm thick, completely covered by yellow wavellite crusts.

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Franckeite [Pb.sub.6][Sb.sub.2]Fe[Sn.sub.2][S.sub.14]

Franckeite occurs in small quantities throughout the Llallagua deposit, primarily as a minor component of pyrite/marcasite replacements of pyrrhotite. It has been found commonly as tabular to platy, brilliantly metallic crystals and thin, black, flexible laminae resembling graphite, usually in association with marcasite and wurtzite. Vuggy masses of franckeite lined with drusy franckeite crystals from 2 to 5 mm are currently the main ore in one portion of the Contacto vein, where franckeite is associated with pyrite, arsenopyrite, wurtzite and rare cylindrite. It also occurs abundantly in the Plata vein. Bandy (1944) reported "heavy crystals" found in the early 1940's in the Inca vein above Level 180, associated with brilliant prismatic crystals of cassiterite.

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Galena PbS

Galena is rare at Llallagua. Bandy (1944) mentioned crystals to 5 mm from the La Loca gallery, 400 meters from the intrusive stock.

Goethite [alpha]-[Fe.sup.3+]O(OH)

Goethite has been found as nodules up to 2 cm in diameter, formed by radiating, brownish black fibrous crystals.

Greenockite CdS

Greenockite is widespread in small quantities as tiny pyramidal crystals, sometimes tightly grouped as thin crusts, and as rare twins. Greenockite from Llallagua (as at other Bolivian deposits) is bright brick-red, resembling vanadinite in color, in contrast to the yellow color typical of other world localities. Specimens with minute red greenockite crystals (0.1 mm) sprinkled on wavellite, quartz, cassiterite or marcasite are now widely distributed in micromount collections. It also occurred as orange, mammillary aggregates to 1 cm on cassiterite and quartz, with variscite and wavellite. Greenockite at Llallagua appears to have been deposited hydrothermally as a late-stage primary mineral, rather than being a decomposition product of cadmian sphalerite; no secondary source of cadmium has been found.

Crystals are typically hexagonal pyramidal and hemimorphic, in some cases with prism faces, and sometimes grouped interestingly in cyclic "tetrapod" twins on (10[bar.1][bar.2]), composed mainly of {10[bar.1]0} prism faces and {50[bar.5]3} pyramids, with tiny c-faces.

Greenockite at Llallagua is widespread in small quantities, in all the veins but especially in the richer ore shoots where it coats marcasite and wavellite. The Forastera vein (Levels 481 and 516), the Riggins vein, the Inca vein, the Bismarck vein (Level 411), the Animas vein and the San Jose vein in particular have all been important sources of specimens (Bandy, 1944).

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Gypsum CaS[O.sub.4]-----2[H.sub.2]O

A few specimens of unusual pseudomorphs of gypsum after tabular fluorapatite crystals to about 3 cm in diameter were found in 2002. Since the pseudomorphs were found adjacent to decomposing pyrite, they probably formed by exposure to acidic sulfate-rich water.

Hagendorfite NaCa[Mn.sup.2+]([Fe.sup.2+], [Fe.sup.3+], Mg)[.sub.2](P[O.sub.4])[.sub.3]

Hagendorfite has been reported from Llallagua by Petrov et al. (2001), on the basis of information on specimen labels. However, confirmation of the source is lacking. Therefore the occurrence at Llallagua must be considered doubtful.

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Halotrichite Fe[Al.sub.2](S[O.sub.4])[.sub.4]-----22[H.sub.2]O

Both halotrichite and pickeringite crystallize as post-mining formations in old galleries. Bandy (1944) observed that they started growing as loose fibrous masses on walls in dry parts of the mine almost immediately after the workings were abandoned, the formations reaching 2.5 cm long after 3 weeks, and up to 20 cm in one year.

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Hematite [Fe.sub.2][O.sub.3]

Rosettes of tabular hematite crystals to 1 cm can be found embedded in slightly metamorphosed red shales within a few hundred meters east of the contact between the shales and the volcanic stock (Bandy, 1944).

Hinsdalite (Pb, Sr)[Al.sub.3](P[O.sub.4])(S[O.sub.4])(OH)[.sub.6]

White, spherical crystal sprays up to 1 mm diameter on drusy franckeite and pyrite from the Dolores Atras Section were recently identified as hinsdalite.

Hisingerite [Fe.sub.2][Si.sub.2][O.sub.5](OH)[.sub.4]-----[H.sub.2]O

Reddish to brown, gum-like amorphous masses of hisingerite are common at Llallagua, sometimes associated with cronstedtite. Hisingerite can be soft and plastic when first found underground, but rapidly becomes hard and very brittle after removal from the mine.

Hubnerite (Mn, Fe)W[O.sub.4]

Red-brown hubnerite crystals, rarely twinned, have been found in superficial parts of some veins (Bandy 1944).

Jamesonite [Pb.sub.4]Fe[Sb.sub.6][S.sub.14]

Jamesonite is widespread as metallic fibers in those veins which transect sedimentary rock. It has even been found as dense inclusions in some younger fluorapatite and vivianite crystals.

Jarosite K[Fe.sub.3](S[O.sub.4])[.sub.2](OH)[.sub.6]

Massive yellow jarosite has been found with limonite in the centers of larger veins, and straw-yellow, compact masses of porcelaneous texture can now be found in oxide-zone material in the upper levels of block-caving rubble. Much rarer are the small brown jarosite crystals found in the Blanca vein.

Jeanbandyite ([Fe.sup.3+], [Mn.sup.2+])([Sn.sup.4+])(OH)[.sub.6]

Jeanbandyite was described by Kampf (1982) and named after Jean Bandy, who had donated her husband Mark Bandy's collection to the Natural History Museum of Los Angeles County. It is orange-brown and forms tiny (0.2 mm), epitactically oriented bipyramidal overgrowths on the corners of yellow octahedrons of wickmanite, in most cases completely enveloping the host crystal. The only forms observed are the pyramid {111} (striated parallel to [100]), pinacoid {001} (parallel to the cube face of the host) and prism {100}. Jeanbandyite is tetragonal pseudo-cubic with extremely low birefringence and cell constants a and c so similar to each other as to be indistinguishable.

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The species was identified on 36 specimens of massive stannite in the Bandy collection, most of which contain prominent crystals of colorless, blocky to tabular fluorapatite to 5 cm. Well-formed crystals of stannite to 2 mm line pockets in this matrix, along with crystals of pyrite, jamesonite, cassiterite, quartz and crandallite. These specimens were collected from large vugs on and above Level 295 of the Contacto vein. Most existing specimens of the mineral were probably collected by Bandy at this location, but jeanbandyite has also been identified on Level 250 of the Contacto vein and Level 295 of the Contacto-Dolores vein, with fluorapatite, stannite and cassiterite. Twelve meters above Level 411 of the Bismarck vein it has been found with wolframite, bismuthinite, stannite and pyrite. And 20 meters above Level 160 of the Plata vein it has been found with franckeite, stannite and pyrite.

Gordon (1944) figured an isotropic octahedral crystal of an unknown species, probably natanite (he cited an index of refraction of 1.745; natanite equals 1.755), with epitactic overgrowths of an unknown tetragonal mineral along the octahedron edges. The tetragonal mineral is similar to jeanbandyite in that it is of low birefringence and uniaxial negative, showing {100} (actually {001}?) parallel to the host cube {100} face and the tetragonal pyramid {111} parallel to the host octahedral {111} face. Gordon indicates a refractive index "similar" to that of the host crystal, 1.745, whereas the indices of jeanbandyite are [epsilon] = 1.833 and [omega] = 1.837. Nevertheless, Kampf (1982) identifies specimens of jeanbandyite overgrowths on natanite from Santa Eulalia, Chihuahua, Mexico, so it is distinctly possible that Gordon's optical measurement was somehow in error.

Jeanbandyite has since been found on the dumps in a completely different paragenesis, as crudely formed orange octahedrons covered by an orange plumbogummite crust, associated with hemispheres of banded "wood tin" cassiterite, quartz, pyrite and muscovite.

Kaolinite [Al.sub.2][Si.sub.2][O.sub.5](OH)[.sub.4]

White kaolinite clay from Llallagua was described by Gordon (1944).

Linarite PbCu(S[O.sub.4])(OH)[.sub.2]

Bandy (1944) described bright blue crusts of a mixture of linarite and caledonite near Level 355 of the Salvadora shaft.

Malachite [Cu.sub.2](C[O.sub.3])(OH)[.sub.2]

Gordon (1944) found malachite needles with azurite on weathered chalcopyrite.

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Marcasite Fe[S.sub.2]

The most interesting Llallagua marcasites are tabular pseudomorphs after pyrrhotite crystals to 20 cm, covered by wavellite, and paper-thin crystals interleaved with equally thin franckeite layers. In Bandy's time, when deeper sulfide-rich levels were being worked, marcasite was abundant, and its decomposition has caused serious problems on specimens in the Bandy collection; luckily, it is much less common in the upper levels which are currently producing specimens.

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Marcasite crystals are plentiful but small, rarely more than about 1 mm in size. They are usually twinned on (101) or (110); the (101) twins are sometimes reticulated with an orientation inherited from the parent pyrrhotite crystal. Epitactic overgrowths of marcasite on pyrite are also known, with the c axis of the marcasite parallel to one of the a axes of the pyrite. Balls of acicular marcasite crystals to 2 cm are also known (Gordon, 1944).

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Melanterite FeS[O.sub.4]-----7[H.sub.2]O

Green melanterite stalactites are common throughout the mine, and rarely melanterite occurs as crystals to 2 cm. The deep blue cuprian variety is often mistakenly called "chalcanthite" by the miners.

Melonjosephite Ca[Fe.sup.2+][Fe.sup.3+](P[O.sub.4])[.sub.2](OH)

Very rare melonjosephite was identified by X-ray diffraction as brown grains and brown-green aggregates on vauxite and under paravauxite from a rich vauxite-allophane pocket found in 2001-2002.

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Metavauxite Fe[Al.sub.2](P[O.sub.4])[.sub.2](OH)[.sub.2]-----8[H.sub.2]O

Metavauxite was described by Gordon (1944) as being colorless, white, or pale greenish white. The acicular crystals are pale green when viewed on end. Individual crystals have a vitreous luster but fibrous aggregates are silky. The transparent to translucent crystals are brittle and rather soft (hardness of about 3). The crystals are striated parallel to the long dimension.

Metavauxite always occurs on wavellite, which encrusts brecciated fragments of porphyry along faults cutting the veins. It is commonly found intimately associated with paravauxite crystals, which in some cases are perched on needles of metavauxite, with the occasional rosette of blue vauxite crystals. One specimen of vauxite noted by Gordon (1944) has colorless, transparent crystals of paravauxite on one side, and white radial aggregates of metavauxite on the other.

Gordon (1944) noted acicular crystals to 2 cm in length, always aggregated into sub-parallel to radial aggregates. Bandy (1944) noted that metavauxite is relatively abundant as loose silky masses in open fractures along a branch of the San Jose vein, on Level 446. He reports that many years previous to 1944, pale green crystals up to 3 cm or more in length had been found on a branch of the San Jose vein on Level 411. In 1986 the Natural History Museum of Los Angeles County acquired a specimen with crystals to 5 cm, though its level of origin within the mine was not noted. In the early 1940's exceptional specimens were found along a branch of the Serrano vein above Level 355, associated with paravauxite and allophane. Open fissures were found coated with thin films of wavellite on which has been deposited (first) paravauxite and (second) metavauxite, both very loosely attached. Metavauxite alters quite readily to a brown to pale yellow, unidentified alteration product and is sometimes stained brown on the surface by iron oxides.

A few very nice specimens with crystals up to 3 cm were found in the summer of 2001; these specimens are among the best known for this species.

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Miargyrite AgSb[S.sub.2]

Miargyrite has been reported from Llallagua by Petrov et al. (2001), on the basis of information on specimen labels. However, the authors believe that the specimens in question are probably mislabeled as to locality, and confirmation of the source is lacking. Therefore the occurrence at Llallagua must be considered doubtful.

Monazite (La, Ce, Y)P[O.sub.4]

Gordon (1944) provided an analysis of Llallagua monazite showing weight percentages of [La.sub.2][O.sub.3] = 33.54, [Ce.sub.2][O.sub.3] = 31.74, and [Y.sub.2][O.sub.3] = 5.13. This may not be as specific as it appears, because La and Ce values may actually refer to groups of elements rather than pure quantities. Small crystals of monazite are widespread in small quantities in all the veins. The largest reported crystals, found embedded in iron sulfides in the Bismarck vein, reach 2.5 cm (Bandy, 1944)! Llallagua monazite often appears pale pink in daylight and deeper pink under tungsten bulbs, but greenish gray to white under fluorescent lighting, an effect caused by a significant content of neodymium. Unlike monazite from other occurrences, Llallagua monazite is practically thorium-free, and therefore hardly radioactive at all; Gordon (1939) reported less than 10 ppm thorium. However, some monazite crystals from Llallagua do contain sufficient traces of thorium to produce an autoradiograph after a three-month exposure. Abundant grains and crude crystals of monazite to 1 cm, associated with white florencite-(Ce) crystals, quartz and pyrite, were found in 1999 in the Dolores Section stope.

Llallagua monazite crystals are typically prismatic, but exaggerrated development of the {[bar.2]11} form can present a pyramidal aspect. Twinning is common, usually on (100), as contact twins and as penetration twins.

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Monazite has been found as masses of crystals to 1 cm in the Salvadora vein; as twins on quartz crystals in the Bismarck vein; and abundantly in vugs in breccia in the Contacto vein. In some parageneses it appears to have formed in place of fluorapatite.

Bandy (1944) reported a rhombohedral dimorph of monazite which might be a new mineral, or which might be rhabdophane.

Ahlfeld (1955) mentions that the best monazite/rhabdophane crystal known was a 2-cm crystal in the collection of Pyotr Zubrzycki, a Polish mining engineer and Chief Geologist for COMIBOL, who had come to Bolivia as a refugee from stalinism. According to a story told to us by Dr. Fritz Berndt (berndtite), Zubrzycki panicked during the Bolivian revolution of 1952, mistakenly imagining that all the horrors of stalinist eastern Europe were about to be perpetrated on him again, and he ran away to Canada. Before escaping from Bolivia, he entrusted his fine Bolivian mineral collection to a humble miner, who buried it in the ground inside his earthen-floored hut, and nothing more has been heard of this collection since.

Muscovite K[Al.sub.2]Al[Si.sub.3][O.sub.10](OH)[.sub.2]

Fine-grained muscovite ("sericite") is the second most common mineral in the deposit, after quartz. It originated by massive sericitization of feldspars. Massive muscovite ("pinnite") forms pseudomorphs after cordierite crystals in granodiorite pegmatites. Red micaceous crystals and aggregates found recently on a dump, filling fissures in narrow quartz-cassiterite veins, have been analyzed as muscovite.

Nacrite [Al.sub.2][Si.sub.2][O.sub.5](OH)[.sub.4]

Nacrite (the monoclinic polymorph of kaolinite and halloysite) was tentatively identified in vugs by Mark Bandy (1944) as white hexagonal-tabular microcrystals with pearly luster, especially in younger veins. It can still be found on some cassiterite and quartz specimens, often with monazite-(Ce), and as radiating spheres on franckeite.

Natanite [Fe.sup.2+][Sn.sup.4+](OH)[.sub.6]

Natanite occurs extremely rarely as pale yellow, translucent, sharp simple octahedrons to 0.2 mm on quartz and pyrite from the Dolores Atras Section. Gordon (1944) figured a brown, isotropic, octahedral crystal of an unknown species, probably natanite (he cited an index of refraction of 1.745; natanite equals 1.755), with epitactic overgrowths of an unknown tetragonal mineral along the octahedron edges, possibly jeanbandyite (q.v.).

Opal Si[O.sub.2]-----n[H.sub.2]O

Opal formed by hot springs is known from several sinter deposits around the stock, for example at Uncia. Greene (1943) reported opal pseudomorphs after quartz crystals at Llallagua.

Orpiment [As.sub.2][S.sub.3]

Orange-yellow orpiment coating quartz was described by Gordon (1944). It originated from weathered arsenopyrite.

Paravauxite Fe[Al.sub.2](P[O.sub.4])[.sub.2](OH)[.sub.2]-----8[H.sub.2]O

Paravauxite was described by Gordon (1923), along with vauxite.

It is the most common of the three "vauxites" (the other being metavauxite) and sometimes forms large masses of crystals in vugs. The characteristic brittle, vitreous, transparent to translucent triclinic crystals are pale green when large and colorless when small. The crystal habit resembles that of gypsum, in individual crystals to 1 x 2 cm which are prismatic to tabular on (010), with perfect cleavage parallel to (010). Paravauxite almost always occurs as individual crystals perched on wavellite encrusting quartz in the tin veins and porphyry breccia fragments in the fault zones. It has been found on crusts of blue vauxite in the fault zones, and as crystals perched on metavauxite needles. Childrenite has often been observed in association with paravauxite on wavellite. Although radial to subparallel aggregates are known, paravauxite shows much less tendency toward radial aggregation than vauxite or metavauxite (Gordon, 1944). Surface oxidation can turn the crystals pale yellow. White opaque crystals have been shown to be pseudomorphs of sigloite after paravauxite.

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Bandy (1944) reported that fine, colorless crystals of paravauxite coating wavellite had been found in the stock, 70 meters from the contact, along the San Jose vein on Level 650. But the finest specimens from the early 1940's were found in vugs along the Contacto vein in the sediments on Level 411, 400 meters from the contact. These vugs were lined with wavellite on which had grown paravauxite crystals and later childrenite, which preferentially coated the exposed wavellite. Greenish paravauxite crystals were also found in vugs in wavellite. On Level 516 in the Contacto vein, about 550 meters from the contact, Bandy (1944) reports a similar occurrence of paravauxite except that it had been coated by childrenite and then had dissolved away, leaving childrenite shells. In the 1930's crystals to 3 cm were found on Level 411, along a branch of the Serrano or San Jose vein, and the mineral was common as greenish crystals on allophane along the Bismarck vein near the contact on the same level.

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There have been several recent, fairly abundant discoveries of paravauxite, with some specimens showing splendid pale green crystals to 3 cm.

Pickeringite Mg[Al.sub.2](S[O.sub.4])[.sub.4]-----22[H.sub.2]O

Pickeringite was identified by Bandy (1944) as a post-mining formation in old galleries, together with halotrichite.

Plumbogummite Pb[Al.sub.3](P[O.sub.4])[.sub.2](OH, [H.sub.2]O)[.sub.6]

Specimens showing pale yellow mammillary or microbotryoidal crusts of plumbogummite on drusy quartz and cassiterite in fissures are found fairly commonly on some dumps. The authors have found somewhat more interesting specimens in which plumbogummite forms orange shells around crude octahedral jeanbandyite crystals.

Potoslite [Pb.sub.6][Sn.sub.2.sup.4+][Fe.sup.2+][Sb.sub.2.sup.5+][S.sub.16]

Potoslite has been reported from Llallagua (www.mindat.org), as being unconfirmed and therefore doubtful.

Pyrargyrite [Ag.sub.3]Sb[S.sub.3]

Pyrargyrite probably does not occur in the Llallagua stock, but it was an ore mineral with galena in a peripheral vein in graywackes at Uncia, 3 km south of the intrusion.

Pyrite Fe[S.sub.2]

Pyrite is very common as beautiful, sharp, octahedral, cubic or cuboctahedral crystals (but never as pyritohedrons). It appears also as pseudomorphs after pyrrhotite and, rarely, after teallite and feldspar. Pyrite crystals from some weathered dumps exhibit peculiar tunnels or serpentine "worm holes" etched into them; the finest specimens of this kind were found around the periphery of the main mineralization zone. Nice pyrite crystals to 7 cm were found recently as floaters embedded in soft, massive franckeite in the Dolores Section stope.

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Pyromorphite [Pb.sub.5](P[O.sub.4])[.sub.3]Cl

Green pyromorphite crystals were found in an oxidized vein 1.7 km east of the southern end of the stock (Bandy, 1944).

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Pyrrhotite [Fe.sub.1-x]S

Pyrrhotite was widespread as hexagonal, tabular to barrel-shaped prismatic crystals, but almost all of the original pyrrhotite has been replaced by pyrite and marcasite. Pseudomorphic crystals can reach 15 cm, and some are covered by a wavellite crust. Bandy (1944) mentioned a portion of the Contacto vein on Level 516 where unaltered pyrrhotite formed masses 2 meters across.

Quartz Si[O.sub.2]

Quartz is the most common mineral at Llallagua, in crystals reaching 10 cm in length. Many of the quartz specimens are encrusted by wavellite. Flattened Japan-law twins are frequently found in the centers of veins. Transparent quartz crystals commonly show tiny inclusions of metallic minerals such as arsenopyrite or pyrrhotite, and occasionally wolframite; Bandy (1944) described cassiterite crystals and tourmaline embedded in quartz. Yellow-orange inclusions of monazite or xenotime up to about 2 mm are very rare. One metallic acicular crystal included in quartz was determined by X-ray diffraction and X-ray fluorescence analysis to be a mineral close to gustavite (PbAg[Bi.sub.3][S.sub.6]).

Realgar AsS

Acicular microcrystals of realgar are occasionally seen coating arsenopyrite; one mass of native arsenic and gypsum shows lamellae of realgar. The species is thought also to constitute the coloring matter in Llallagua's pink sphalerite.

Rhabdophane? (La, Ce, Y)P[O.sub.4]-----[H.sub.2]O

Bandy (1944) cited an undescribed species which he thought to be a rhombohedral analog of monazite; he suggested it should be named "llallagualite." It was found in vugs along the Plata vein on Level 190, in crystals to 3 mm showing the base and two rhombohedrons. Unfortunately it has never been confirmed as a new species (thereby precluding the formal naming of any other new species in honor of this famous locality), and Bandy's specimens of it cannot be found. Clark (1993) suggested that the mineral may be rhabdophane.

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Rhodochrosite MnC[O.sub.3]

Llallagua is the only Bolivian locality which has yielded good rhodochrosite crystals. The attractive pink rhombohedrons, to 1 cm, are found rarely in vugs with wurtzite and sphalerite. Gordon (1944) depicts equant crystals whose complex faces lend them an almost rounded habit; the faces include {0001}, {11[bar.2]1}, {[bar.1][bar.1]22}, {81[bar.9]1}, {[bar.2][bar.2]41} and {32[bar.5]0}. Rhodochrosite also occurs as veinlets in masses of iron sulfides. Some Llallagua rhodochrosite is pale brown rather than pink, and so is difficult to distinguish from siderite.

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Romerite [Fe.sup.2+][Fe.sub.2.sup.3+](S[O.sub.4])[.sub.4]-----14[H.sub.2]O

Ahlfeld and Munos Reyes (1955) reported romerite as crusts of rust-brown crystals in old workings, associated with chalcanthite, melanterite and pickeringite.

[FIGURE 86 OMITTED]

Rutile Ti[O.sub.2]

Tiny crystal grains of rutile are common in the igneous rocks as well as in surrounding sediments. Some of the rutile might be of hydrothermal origin, according to Turneaure (1935). It also occurs as tiny (0.5 mm) black to brown crystals in cavities in muscovite; the prismatic crystals are easily mistaken for cassiterite. Geniculated and reticulated twins are common.

[FIGURE 87 OMITTED]

Scheelite CaW[O.sub.4]

Tiny orange, bipyramidal scheelite crystals were identified by Gordon (1944) on one specimen from Level 435 of the San Jose vein.

Siderite FeC[O.sub.3]

As in most Bolivian mines, siderite at Llallagua is by far the most abundant carbonate gangue mineral, especially in younger veins and on the periphery of the deposit (although crystals are much less common here than in other Bolivian tin mines). Nice rhombohedral crystals have only rarely been found. Siderite, in massive veins and in brown, prismatic microcrystals and subparallel aggregates, is associated with iron sulfides, sphalerite, franckeite and wurtzite. Siderite pseudomorphs after fluorapatite were reported by Gordon (1944).

Sigloite Fe[Al.sub.2](P[O.sub.4])[.sub.2](OH)[.sub.3]-----7[H.sub.2]O

Sigloite was described by Hurlbut and Honea (1962) as white or yellowish, opaque pseudomorphs after paravauxite, sometimes resting on orange childrenite. This is probably the same material that Bandy referred to as "hydrated paravauxite" (Bandy, 1944). Some so-called "sigloite" on the mineral market is actually misidentified childrenite. Crusts of pale brown sigloite crystals have been found quite commonly, but were often discarded in the past as merely "weathered paravauxite."

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Silver Ag

A specimen with native silver coating small tetrahedrite crystals is mentioned by Gordon (1944), but it is not certain whether it really came from Llallagua. It is feasible that the specimen could have come from one of the peripheral pyrargyrite-bearing galena veins.

Sphalerite ZnS

Sphalerite is common at Llallagua, in crystals to 1 cm, commonly wholly or partially replaced by younger stannite. Abundant small crystals of brown-black iron-rich sphalerite are occasionally found growing on the faces of larger pyrite crystals. Herzenberg (1933) described raspberry-red nodular to reniform masses of an arsenic-bearing sphalerite (0.64 weight % As) of colloidal origin, calling it gumucionite after Julio Gumucio, who was then chief mining engineer at Llallagua and is the only native-born Bolivian to have assembled an important mineral collection. (It was discredited as a mixture of sphalerite and realgar in 1970.) Pale pink to pale orange sphalerite masses of porcelaneous texture (looking not at all like sphalerite!) form part of the matrix in recently collected vivianite specimens.

Stannite [Cu.sub.2]FeSn[S.sub.4]

Stannite is much less common at Lllallagua than at Oruro, but its few surviving specimens are very probably the world's best for the species, even better than the new Chinese specimens from Yaogangxian. The best specimen is perhaps the one preserved at Harvard University, and an excellent specimen from Mark Bandy's collection is exhibited at the Natural History Museum of Los Angeles County. Sharp microcrystals of stannite can be found on some of the franckeite specimens collected in the 1990's.

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Stannite at Llallagua is black to brownish steel-gray and usually massive. Crystals, when found, tend to be striated, with dull faces, and are sometimes twinned on (111) resulting in spinel-like twins and polysynthetic laminations. Less commonly, twinning on (011) results in triplets resembling simple cuboctahedra but with striated or sutured surfaces on {111}. A bluish to bronzy red or green tarnish is often present, and the association with sphalerite (which it resembles and sometimes replaces) can serve to distinguish it. Though stannite is tetragonal, the crystal forms {001}, {100}, {1[bar.]11} and {111} commonly combine to simulate a cuboctahedron.

Stannite is most abundant in the southern third of the stock, especially in the upper portions of veins; the largest masses have been found in the Plata vein and its branches. Brilliant, well-developed crystals were found near the junction of the main Plata vein and Branch A, about 15 meters above Level 160. A large apatite-lined vug on Level 295 yielded abundant stannite crystals as well as sphalerite and prismatic cassiterite. Lustrous, well-formed crystals have also been found along the Bismarck vein, above Level 411, and stannite was locally abundant in the San Jose/San Fermin and Victoria veins as well. Franckeite and cylindrite are almost invariably associated with some stannite (Bandy, 1944).

Bandy (1944) reported that the prominent Bolivian mine owner and mineral collector Hans Block (a close associate of Frederick Ahlfeld) had in his collection exceptionally large crystals of stannite, to over 4 cm long and 2.5 cm in diameter, from the Salvadora vein, Level 1260. They were associated with equally large crystals of sphalerite, franckeite and rods of cylindrite.

Stibnite [Sb.sub.2][S.sub.3]

Some gray acicular crystals are thought to be stibnite, though it is impossible to definitely identify by sight (Bandy, 1944). Gordon (1944) described masses of stibnite with orange-yellow stibiconite. It was abundant in the Angela mine, 7 km north of the intrusive stock (Bandy, 1944).

Sulfur S

Sulfur is found as minute yellow crystals, usually with bismuthinite or marcasite. According to Bandy (1944), some of this sulfur may be of primary origin, though Gordon (1944) believed it to be an alteration product of bismuthinite. Gordon (1944) depicts a sulfur crystal, rich in complex faces, found on marcasite on Level 446 of the San Pedro vein.

Teallite PbSn[S.sub.2]

Teallite has been reported from Llallagua by Petrov et al. (2001), on the basis of information on specimen labels. However, the authors believe that the specimens in question are probably mislabeled as to locality, and confirmation of the source is lacking. Therefore the occurrence at Llallagua must be considered doubtful.

[FIGURE 92 OMITTED]

Tenorite CuO

Gordon (1944) found black massive tenorite with chalcanthite in the Rosas vein.

Tetrahedrite [Cu.sub.3]Sb[S.sub.3]

Small, black, tetrahedral crystals of tetrahedrite, usually twinned, occur with stannite and sphalerite at Llallagua.

Tetradymite [Bi.sub.2][Te.sub.2]S

Tetradymite was described by Turneaure (1935) as inclusions in bismuthinite from the Contacto vein, Level 446.

Thorite ThSi[O.sub.4]

Frondel (1958) reported thorite from hydrothermal sulfide veins in Llallagua, but this needs confirmation.

Tourmaline Group

A black mineral of the tourmaline group is one of the most common Llallagua species, because sericitization of feldspars was followed by tourmalinization, and practically all of the original feldspar in the porphyry was replaced by fine-grained tourmaline. Bandy (1944) reported tourmaline constituting up to 90% of black "breccia dikes" in the stock. Tourmaline also formed in the metamorphosed sediments around the stock. This process made the Llallagua intrusion one of the world's largest accumulations of tourmaline, although most of it occurs as felty or fibrous microcrystal masses and none of it is in the form of collector-quality crystals. Pseudomorph collectors may find the tourmaline pseudo-morphs after Carlsbad twins up to 8 cm to be beautiful, and these can still be found on dumps and on the top of Cerro Salvadora. Micromounters will find acicular crystals, in several colors ranging from colorless to pale blue, pale green, greenish yellow and pale brown to brownish gray, in vugs in the altered volcanic stock, sometimes impaling spheres of younger phosphates.

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Troilite FeS

Troilite, usually thought of as a meteoritic mineral, was identified by Gordon (1944) at Llallagua as extremely small crystals to 0.25 mm in tiny vugs in porphyry adjoining the San Jose vein. The sharp, tabular, rhombohedral crystals are yellow with a brilliant metallic luster.

Tungstite W[O.sub.3]-----[H.sub.2]O

Massive yellow tungstite (?) was found with wolframite in the oxidation part of the Blanca vein (Bandy, 1944).

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Variscite AlP[O.sub.4]-----2[H.sub.2]O

Gordon (1944) depicts colorless tabular variscite crystals with large c-faces {001} bounded by the prism faces {010}, {100} and {120}, bevelled by small {111} faces. Normally, variscite at Llallagua forms green-blue to blue and bluish white, smooth spherules with radial internal structure and waxy or glassy surface luster. Specimens showing variscite spherules perched on acicular tourmaline needles, and on quartz crystals in vugs left by the dissolution of orthoclase crystals in the porphyry, are still found commonly on the dumps. Pale blue waxy spherules of variscite on native bismuth were found underground in the early 1990's.

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Vauxite Fe[Al.sub.2](P[O.sub.4])[.sub.2](OH)[.sub.2]-----6[H.sub.2]O

Vauxite was described for the first time by Gordon (1923). Sky-blue to Venetian-blue crusts of tiny, vitreous, transparent, tabular vauxite crystals were found in almost all of the veins when Gordon visited Llallagua in the 1920's and again by Bandy in the 1940's. According to Bandy (1944) it generally occurs in sediments and in the stock near the contact with sediments. In the early 1940's the finest specimens were found lining open fissures on the footwall and hanging wall of the San Jose vein above Level 446. In one particularly large fissure in the footwall fine crystals in spherical aggregates were found perched on quartz, wavellite, marcasite and other minerals, associated with minor paravauxite. Small amounts were also found along the Contacto vein up to 400 meters from the stock. Fine specimens of vauxite on paravauxite were collected from a branch of the Serrano vein just east of the San Jose vein, above Level 446. However, on a branch of the San Jose vein on Level 446 Bandy (1944) found the reverse: metavauxite on vauxite. Fine specimens have also been recovered from the Bismarck vein. Vauxite has been seen on all levels below Level 383, and one fine specimen was collected higher up on Level 205.

Drusy vauxite commonly formed on mammillary allophane, which crumbles to powder upon dehydration, leaving a thin crust of pure vauxite with rounded impressions on the back. Radial aggregates forming nodules to 1 cm across were found in the early 1940's in the San Jose/San Fermin vein, on wavellite crusts covering quartz crystals (Gordon, 1944). It is also found on wavellite crusts covering porphyry breccia fragments in fault zones, and as thin but solid crusts covering paravauxite crystals. It has also been found rarely on cassiterite crystals in vuggy tin ore. The triclinic crystals are tabular on (010), and some are also twinned on (010).

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Although Turneaure (1935) regarded the "vauxites" to be of supergene origin, Bandy (1944) considered them to be hypogene, with vauxite as the youngest mineral to form in the sequence wavellite[right arrow]metavauxite[right arrow]paravauxite[right arrow]vauxite.

Very nice blue druses of vauxite were found again in the summer of 2001, accompanied by pearly white allophane and pink crandallite. Spheres of vauxite microcrystals are much rarer, but are sporadically found on quartz and cassiterite. Very beautiful greenish blue to bright blue spheres with diameters to about 3 cm were found in 2003. Surprisingly, yellowish brown to greenish brown crystals from this new find were shown by X-ray diffraction to be vauxite as well; apparently a very minor amount of oxidation is enough to change the color from blue to green-brown.

Vivianite Fe(P[O.sub.4])[.sub.2]-----2[H.sub.2]O

Before the famous discoveries of vivianite crystals at Morococala and Huanuni in the 1980's and 1990's, Llallagua was the source of the world's best vivianite specimens. Some of the biggest doubly terminated crystals were found in clay and reached 2 x 2 x 7 cm. Gordon (1944) reported extraordinarily perfect and beautiful, transparent, bottle-green crystals to 10 cm from the San Jose/San Firmin vein. In general the vivianite occurs on a matrix of botryoidal goethite derived from the alteration of pyrite and marcasite. The crystals are prismatic in habit, with a tendency toward parallel growth.

Surprisingly nice specimens were found in 2000; they show transparent, triangular tabular crystals up to 13 cm across, in many cases arranged in parallel rows like saw teeth, associated with childrenite, cronstedtite, pyrrhotite, franckeite and pink massive sphalerite.

Wavellite [Al.sub.3](P[O.sub.4])[.sub.2](OH, F)[.sub.3]-----5[H.sub.2]O

Wavellite is one of the most abundant Llallagua minerals, occurring usually as white or pale yellow coatings, crusts and radial aggregates on quartz and cassiterite druses. Llallagua wavellite can be colorless, white or pale yellow, and rarely orange or pale grayish green, but is never bright green like the Arkansas specimens. Colorless single crystals up to 5 mm have been commonly found in the deeper parts of the mine, below Level 383. Bandy (1944) observed a rough correllation between crystal size and depth. Quartz is sometimes covered by wavellite spheres with a radial structure, to 4 cm in diameter. Fine druses of wavellite invariably form the substrate for the growth of large crystals of vauxite, paravauxite, childrenite and large crystals of wavellite. Wavellite also forms pale orange epimorphs after large tabular fluorapatite crystals.

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Wavellite crystals, at least the better-formed ones, are transparent to translucent and colorless to pale green or pale yellow, with a vitreous luster (sometimes pearly on the prism faces). Crystals are prismatic to tabular on (010), with a perfect cleavage parallel to (110).

The San Jose vein on and above Level 650 has produced the most good specimens, with crystals to 4 mm. A few doubly terminated crystals have been found in the Uno A vein on Level 481. Most of the good specimens of wavellite in spherical clusters (to 3 cm in diameter) have come from the lower levels of the San Jose vein; the surface of these spheres is composed of crystal terminations. The finest specimens have come from quartz-lined vugs lacking any other associated minerals. Attractive yellow spheres have been found in the San Miguel vein, Level 383, and the San Jose vein, Level 620. Wavellite coating quartz with a thin film of red greenockite and black sulfides came from the Reggis and Forastera veins below the sulfide horizon. The Contacto vein below the sulfide horizon also contains quartz crystal vugs thickly covered by drusy wavellite. Small pellets to 3 mm are found throughout the mine (Bandy, 1944).

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Nice yellow wavellite spheres to 1 cm in diameter with fluorapatite crystals on quartz were found in 2002.

Wickmanite MnSn(OH)[.sub.6]

Tiny yellow octahedral crystals of wickmanite were identified by Kampf (1982) as the host crystals for epitactic overgrowths of orange-brown jeanbandyite crystals.

Wurtzite ZnS

Well-formed, tabular to blocky, brilliant brownish black wurtzite crystals are famous from several Bolivian deposits, and are not uncommon in the secondary veins at Llallagua. Crystals of wurtzite to several centimeters were said to have been found in the early days at Llallagua, but few were preserved. Wurtzite at Llallagua forms rosettes of tabular crystals, large and fine hemimorpic crystals, fibrous masses, and interlaminations in marcasite/pyrite replacements of pyrrhotite, associated with galena, franckeite and a carbonate (siderite or rhodochrosite). Wurtzite replacements of pyrrhotite developed along basal parting planes and so the resulting pseudomorphs tend to retain the original orientation. In vugs, wurtzite forms subparallel to radial aggregates and individual crystals to 2 cm or more. Most wurtzite crystals have inverted to sphalerite (Gordon, 1944).

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Fibrous wurtzite occurred in some of the north-central veins between Level 383 and Level 516, as coatings on sphalerite. Tabular crystals and rosettes were found in vugs in the upper levels of the Contacto vein, associated with sphalerite, wolframite and franckeite. Large hemimorphic crystals to 1 x 1 cm were found perched on a layer of franckeite on Level 190 south of the Plata vein. Good crystals to 3 mm on brilliant crystals of marcasite have been found on the San Pedro vein, above Level 446 (Bandy, 1944). Ahlfeld and Munos Reyes (1955) also described fine crystals from the Salvadora vein, associated with franckeite, wavellite and vauxite. A specimen composed entirely of black wurtzite crystals up to 1 cm and weighing 600 grams is in a private German collection. A few tapering, pagoda-like crystals to 2 cm were found in vugs in pyrite in the Dolores Section in the mid-1990's.

Xenotime-(Y) YP[O.sub.4]

Dark yellow prismatic xenotime-(Y) crystals are much rarer at Llallagua than the associated monazite crystals. Rarely, both species form inclusions in quartz. Gordon (1944) cited crystals up to only 1 mm, and Ahlfeld and Munos Reyes (1951) described xenotime-(Y) crystals reaching only 2 mm, but at least one fantastic Llallagua specimen is exhibited in the Natural History Museum in London. It is a 4 x 7-cm matrix covered by yellow monazite crystals to about 9 mm, with smaller, pale green xenotime-(Y) crystals. Bandy (1944) reported good crystals from the Bismarck vein (between Levels 411 and 383), as well as several places on the Animas branch M vein (between Levels 305 and 215).

Zinkenite [Pb.sub.9][Sb.sub.22][S.sub.42]

Zinkenite has been reported from Llallagua by Petrov et al. (2001), on the basis of information on specimen labels. However, the authors believe that the specimens in question are probably mislabeled as to locality, and confirmation of the source is lacking. Therefore the occurrence at Llallagua must be considered doubtful.

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CURRENT COLLECTING POSSIBILITIES

Llallagua is a cooperativa (meaning that it is jointly owned by the miners themselves) presently being worked by many thousands of very poor miners, who are laboring under very primitive conditions. They exploit the remains of tiny cassiterite veins underground, or rework old dumps. Only a few of them have any idea what a mineral specimen for a collection should look like; accordingly, some of the workers keep broken druses of quartz with cassiterite as decorations at home, but well preserved specimens are rare.

When the authors visited Llallagua for the first time together on a Saturday in 1993, we asked several miners for mineral specimens. The answer was always the same: "You are lucky, today is concentration day." We didn't understand until people brought us sacks full of powdered cassiterite, and whined "But why don't you want it? It's so pure!" We were not able to get even one specimen during this first visit. Since then, a few miners have learned about the specimen market, and small lots of crystallized specimens, mostly phosphates, occasionally appear at mineral shows.

The good news is that visitors can go field collecting on the enormous dumps. The authors have found nice pseudomorphs of tourmaline after feldspar and pyrite after feldspar. We have also found vugs with crystals of monazite, wavellite, florencite-(Ce), cassiterite, jeanbandyite and other species. Other interesting minerals are certainly still waiting to be found on the dumps, but these will delight mainly micromounters, as the chances of digging a nice cabinet specimen out of the dumps are close to zero.

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For a modest remuneration, and with permission from whichever cooperativa office is responsible for the Section one wishes to enter, Spanish speakers can arrange to accompany a miner underground to a working stope. Be forewarned that Siglo XX is dangerous underground. A friend of the authors died recently during a bumpy ride to the hospital after having broken multiple bones falling down a rotten ladder. You will get dirty and may encounter extreme temperatures, both hot and cold; safety rules will not be observed, you will not be able to sue anyone if you get injured, and you might have to stay underground for your miner's entire shift, as you might not be able to find your way back to the surface by yourself.

ACKNOWLEDGMENTS

Our thanks to William Larson of Pala International, Rock Currier of Jewel Tunnel Imports, Dr. Anthony Kampf of the Natural History Museum of Los Angeles County, Dr. Paul Bartos of the Colorado School of Mines Geology Museum, and Jeff Scovil for supplying additional photography for this article. We especially wish to thank Dr. Wendell Wilson for additional photography and for hunting down numerous additional historical sources. The text was reviewed by Drs. Anthony Kampf and George Robinson, who made numerous helpful suggestions.

BIBLIOGRAPHY

AHLFELD, F. (1929) Die Zinnerzgrube Uncia-Llallagua (Bolivia). Metall und Erz, 26 (14), 349-354.

AHLFELD, F. (1931) The tin ores of Uncia-Llallagua. Economic Geology, 26, 241-257.

AHLFELD, F. (1936) The tin deposits of Llallagua, Bolivia (disc.). Economic Geology, 31, 219-221.

AHLFELD, F. (1941) Los Yacimientos Minerales de Bolivia. Direccion General de Minas y Petroleos, La Paz, 94-100.

AHLFELD, F. (1941) Zoning in the Bolivian tin belt. Economic Geology, 36, 569-588.

AHLFELD, F. (1954) Los Yacimientos Minerales de Bolivia. El Banco Minero de Bolivia y la Corporacion Minera de Bolivia, 2nd edition, Bilbao, 63-67.

AHLFELD, F., and MUNOZ REYES, J. (1955) Las Especies Minerales de Bolivia. Banco Minero de Bolivia, La Paz, Bolivia. 180 p.

AHLFELD, F., and SCHNEIDER-SCHERBINA, A. (1964) Los Yacimientos Minerales y Hidrocarburos de Bolivia. Departamento National de Geologia, Bolivia, Boletin 5, 388 p.

ANTHONY, J. W., BIDEAUX, R. A., BLADH, K. W., and NICHOLS, M. C. (1997) Handbook of Mineralogy. Vol. III: Halides, Hydroxides, Oxides. Mineral Data Publishing, Tucson, 278.

ARZRUNI, I. (1884) Ueber einige Mineralien aus Bolivia. Zeitschrift fur Krystallographie, 9, 73.

BANDY, M. C. (1944) Mineralogy of Llallagua, Bolivia. La Paz (reprinted by Tucson Gem and Mineral Society in 1976 as "Special Publication No. 1"). Available from the Natural History Museum of Los Angeles County; see page 190 for contact information.

CLARK, A. M. (1993) Hey's Mineral Index. Chapman and Hall, London, 405.

DAVY, W. M. (1920) Ore deposition in the Bolivian tin-silver deposits. Economic Geology, 15, 463-496.

DERINGER, D. C., and PAYNE, J. Jr. (1937) Patino, leading producer of tin: I. The ore deposits of Llallagua. Engineering and Mining Journal, 138, 171-177, 232-238.

FRONDEL, C. (1958) Systematic Mineralogy of Uranium and Thorium. USGS Bulletin 1064, p 275.

GORDON, S. G. (1923) Vauxite and Paravauxite, two new minerals from Llallagua, Bolivia. Proceedings of the Academy of Natural Science, Philadelphia, 75, 261-267.

GORDON, S. G. (1939) Thorium-free monazite from Llallagua, Bolivia. Academy of Natural Science, Philadelphia, Notulae Naturae, no. 2.

GORDON, S. G. (1944) The mineralogy of the tin mines of Cerro de Llallagua, Bolivia. Proceedings of the Academy of Natural Science, Philadelphia, 96, 279-359.

GREENE, G. U. (1943) Collecting minerals at Llallagua, Bolivia. Rocks & Minerals, 18, 291-294.

HERZENBERG, R. (1933) Gumucionit, eine neue arsenhaltige Varietat der Schalenblende. Centralblatt fur Mineralogie A, 77-78.

HURLBUT, C. S., and HONEA, R., (1962) Sigloite, a new mineral from Llallagua, Bolivia. American Mineralogist, 47, 1-8.

HYRSL, J., and PETROV, A. (1996) Potosi und Oruro, die bedeutendsten Silberlagerstatten Boliviens. Mineralien-Welt, 7 (6), 36-49.

HYRSL, J., and PETROV, A. (1998) Pseudomorphs from Bolivia, A Review. Rocks & Minerals, 73 (6), 410-414.

JONES, R. W. (1973) The Mark Chance Bandy collection. Mineralogical Record, 4, 277-281.

KAMPF, A. R., (1982) Jeanbandyite, a new member of the stottite group from Llallagua, Bolivia. Mineralogical Record, 13, 235-239.

MONTGOMERY, A. (1973-1975) An American mineralogist [Sam Gordon]. Mineralogical Record, 4, 256-261; 5, 34-39; 5, 59-66; 5, 115-127; 5, 160-166; 5, 211-214; 5, 257-264; 6, 7-12; 6, 57-61.

MOON, L. (1939) Structural geology at Llallagua, Bolivia. Minnesota Academy of Science, Proceedings, 7, 64-72.

PETROV, A., SMITH, B., and SMITH, C. (2001) A guide to mineral localities in Bolivia. Mineralogical Record, 32, 457-482.

RAKOVAN, J. (2003) Exceptional apatites from the Siglo XX mine, Llallagua, Bolivia. Mineralogical Record, 34, 1, 117.

RECHENBERG, H. P. (1955) Die Zinnseifenlagerstatte von Llallagua, Bolivien. Berg- und Huttenmannisches Monatshefte, 100 (10), 280-284.

SAMOYLOFF, V. (1934) The Llallagua-Uncia tin deposit. Economic Geology, 29, 481-499.

STELZNER, A. W. (1892) Zeitschrift fur deutschen geologische Gesellschaft, 44, 531-533.

STELZNER, A. W. (1897) Zeitschrift fur deutschen geologische Gesellschaft, 49, 89 and 129.

TURNEAURE, F. S. (1935) The tin deposits of Llallagua, Bolivia. Economic Geology, 30, 14-60, 170-190.

TURNEAURE, F. S. (1960) A comparative study of major ore deposits of central Bolivia. Economic Geology, 55, Part I, 217-254 and Part II, 574-606.

YEATMAN & BERRY (1930) The Mining Journal, supplement, January 25, 41-44.

Jaroslav Hyrsl

Ke kurtum 383

142 00 Prague, Czech Republic

hyrsl@kuryr.cz

Alfredo Petrov

531 N. James Street

Peekskill, New York 10566

alfredopetrov@earthlink.net

RELATED ARTICLE: Sam Gordon at Llallagua, 1925 and 1929

[The following is an excerpt from Sam Gordon's report on his 1925 expedition to Bolivia, published in the Philadelphia Academy of Natural Sciences Yearbook (1926).]

On Monday morning [in Oruro, Bolivia] I worked my way through the dense crowds at the station to the Llallagua train. With much ceremony, a bell was rung, and the train departed. Toward noon we passed the mines of Huanuni, stated to be the first mines worked for tin in Bolivia. It was late in the afternoon when the train reached the mines of Llallagua. These mines produce about fifteen percent of the world's annual supply of tin, as well as considerable bismuth. The tin veins are associated with a large mass of quartz porphyry which has been intruded into a fine-grained red sandstone.

While at Llallagua I made my headquarters at Catavi, the site of the mill, about a league distant from the mines. Daily, after desayuno, or breakfast, I mounted a mule and swung into the trail across the barren, monotonous pampa, broken here and there by an occasional ravine. Just below the mines is the native village of Llallagua, pungent with the odor of burning llama dung from the braziers of the Indian households.

At the main tunnel, the Siglo XX, the chico, or boy, prepared the mine lamps. Seating ourselves on the electric locomotive, we were rushed into the tunnel for a distance of two miles--a trip made in six minutes--to the main shaft. Huge rooms had been cut into the rock, and the walls echoed with the staccato roar of the drill dressers in the blacksmith shop, and the rhythmic boom of the air compressor. Stepping into a cage, we were whisked up to one of the principal levels. Numerous drifts and cross-cuts radiated out to various veins. We walked out along a track, stepping aside now and then to avoid a passing ore car, until we came to a place where we could enter a stope.

To those not familiar with mining methods, a word of explanation of stoping will be necessary. Tunnels are driven along the veins at vertical intervals of a hundred feet. These are roofed over with heavy timber. The ore in the vein is then blasted down onto the roof of the tunnel. At intervals in the roof are chutes through which the ore can be dropped into ore cars. The miners begin at the roof of the tunnel and gradually work upward until all the ore in that section of the vein has been broken up to the next tunnel level, a hundred feet above. Such a working is called a stope.

If a stope has just been started the climb is short. However, where there has been considerable stoping, a climb of 40 or 50 feet may be necessary, or it is sometimes feasible to climb down from an upper level. Several means of access were used, differing in the amount of gymnastics required. We considered ourselves fortunate if there was a series of ladders in various stages of completeness. Missing rungs were frequent, and the reason was apparent. One morning we climbed across a space where a vein had been stoped out. On reaching the opposite end of the ladder we found that it was held in place by a single nail. The next night a fall of rock sent it crashing to the bottom. Sometimes the wooden ladder would be replaced by one of swinging rope. But not infrequently we had to haul ourselves up a rope, bracing the back, knees and elbows against the rock sides. Loud shouts of "Guarde ariba!" ("Look out above!") announced our entry into the raise, so as to avoid being greeted with a shower of rock or drill steel.

[FIGURE 7 OMITTED]

The stopes presented scenes of great industry: Stolid Quechua Indians were operating compressed air drills, or were loading holes with dynamite for the noon or late afternoon blasts. Making our way over the rough floor of broken ore, we carefully examined the face of the vein overhead, and the rock walls on each side. The ore consisted largely of cassiterite, Sn[O.sub.2], in black crystals or masses through quartz, associated with some bismuthinite and wolframite, and much pyrite. Small cavities were lined with twinned crystals of cassiterite. The bismuthinite formed long blades shooting through the pyrite, sometimes with apatite and vivianite. We were surprised at the large amount of the rather rare mineral wavellite, which occurred in druses of colorless crystals covering quartz crystals, or lining fractures along the walls. A single vein of vauxite and paravauxite was found in one stope.

At noon we returned to the surface, and hustled to the dining room, presided over by a smiling Japanese. The meal was enlivened by a discussion of the specimens, and of plans for the afternoon. After eating we wandered over the cancha (mine dumps). Groups of Indian women sat around piles of ore, breaking it up with heavy hammers, and rejecting the worthless material. At one o'clock we re-entered the mine. In a single day from four to seven stopes were visited. At 4:30 p.m. we gathered for tea, which was usually followed by a game of tennis before returning to Catavi.

Some difficulties were encountered in visiting the more remote portions of the mine. The examination of one vein involved climbing down through 875 feet of stopes in a single morning, over 500 feet of which were by ladder. Other veins could only be visited by being lowered down a shaft by means of a steel cable at the end of which were two iron hoops into which the legs were thrust. Descents of 300 feet were made in this manner. In three weeks all of the working stopes were examined in the more than 50 miles of tunnel in the mine. Fifteen cases of specimens were collected, labeled, and packed in steel-strapped boxes. They were then sewn in burlap for shipment.

[The following is an excerpt from one of Gordon's letters to his financial backer for the trips, Mrs. George Vaux, Jr. (widow of Gordon's good friend George Vaux), written during his 1929 expedition to Llallagua.]

My dear Mrs. Vaux,

Bolivia now lies behind me, and the first part of the trip is over. The two months spent there have been extremely fruitful, as is evidenced by sixty-three (63) boxes of specimens, or almost as many as the total number obtained on the last two expeditions to the Andes combined.

The principal minerals have been the vauxite group: vauxite, paravauxite, and metavauxite. Not only has enough material for research work in the chemistry and physical properties of the group been obtained, but also a fine series [of specimens] for both collections. And there are enough choice duplicates of paravauxite to supply all of the collections of the world. The paravauxite and metavauxite are superior to anything obtained before. In fact, the previously collected material is just junk. There are enough fine duplicates, particularly of paravauxite, to pay the entire costs of the expedition so far; and most institutions will be glad to get some of the material.

From Oruro, where I last wrote to you, I went to Llallagua. The mines are much larger now, and there are today over 110 stopes and some 120 miles of workings. In the three and a half weeks here I went pretty thoroughly through the mine. You remember that last fall the assistant mine superintendant brought up some specimens. Well he has been keeping his eye open since then. The General Manager told him I was coming to Bolivia, so he renewed his efforts, most commendably, to gather specimens. He told the metallurgist, "Gordon is coming down next month, and I have the finest collection of vauxite, paravauxite and metavauxite in the world; and if he wants it he will have to come across with $1000." He stated that he knew where there was another big vug that he was going to empty.

The metallurgist then asked a young engineer he knew who had charge of a richly mineralized section of the mine if he had seen any paravauxite in the mine. Sure, he knew where there was a fine vug of the mineral. It seems that the engineer had seen the assistant mine superintendant stop there and dig out a specimen. So the young engineer got busy and filled up half a dozen boxes of vauxite. Then I came along. He told me a story about how some former workman had found it and wanted to sell it, [while] keeping secret which part of the mine it was found in. After a couple of days (during which he steered me away from this section of the mine) I bought his lot for $103. It was wonderful stuff, and although I felt that I might come across the vug myself later, I wanted to gather in every scrap to avoid any of it getting to Ward's or any other institution.

The next day, after I had packed up the previous purchase, he said that the man had brought in another lot. This was somewhat better, and I bought it for $175. Meanwhile I steered clear of the assistant mine superintendant, and bided my time before attempting to purchase his vivianite, metavauxite and vauxite. He realized that his competition had ruined his price. I got his stuff toward the end for less than $350, or about a third of his original price.

So, having cleaned these fellows out, and gone pretty well through the mine, I decided to look for the lost paravauxite vug. One day the young engineer said he was not going into the mine. So at 9 o'clock I headed for his section, picking up a boy at his office to carry the bag. I knew about where the cross-vein should be, and felt quite sure it was on the 195 level. Within half an hour I had found it. The engineer thought he had cleaned it out. Several large chunks of rock blocked up the entrance. After an hour's work I had it well opened up, in such shape as to get out some fine specimens. When I left Llallagua, I shipped 49 boxes of specimens back to Oruro.

doubtful.
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Author:Hyrsl, Jaroslav; Petrov, Alfredo
Publication:The Mineralogical Record
Geographic Code:3BOLI
Date:Mar 1, 2006
Words:15752
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