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Peruvian minerals: an update.

The Peru Issue, published in 1997, surveyed the history, productivity and mineralogy of the most important Peruvian mines and mining districts. Since that time, famous localities such as Pasto Bueno, Pachapaqui, Uchucchacua, and Huanzala, as well as lesser-known mining areas, have yielded a wide range of new collector-quality mineral specimens. In addition, some significant new occurrences have been discovered. We provide here a specimen-recovery update for 1997-2002.

Introduction

Peru is a distant country for most mineral collectors, but it has nevertheless been one of the most interesting mineralogically, especially in recent years. An excellent survey of important Peruvian mines and minerals by Crowley et al. (1997) clearly demonstrated the mineralogical richness of this country. Happily, fine mineral specimens have continued to be found in Peru since that time; our purpose here is to survey the productivity of the most important sites in recent years and describe some of the more interesting discoveries made between 1996 and 2002 (see also our five articles in the German magazine Mineralien Welt, 1999-2002). The order of the localities is the same as that followed by Crowley et al. (1997).

Quiruvilca

The Quiruvilca district, in the Department of La Libertad in northern Peru, is especially famous for its orpiment crystal specimens, often with fine black hutchinsonite crystals. However, the locality has produced few interesting minerals recently. The newer specimens of arsenopyrite, enargite, and cogwheel-twinned bournonite do not reach the quality attained earlier.

Gebhard and Schluter (1998) determined that some unusual crystals on older specimens from Quiruvilca, previously thought to be enargite, are in fact the world's finest crystals of luzonite and famatinite. Luzonite forms tetragonal bipyramidal crystals to 1 cm covered by small tetrahedrite crystals; it has also been identified as tabular reddish violet metallic crystals to 4 cm with cores of enargite. Famatinite forms red-violet crystals to 3 cm, completely covered by small tetrahedrite crystals. Interestingly, luzonite, famatinite and enargite all grow on pyrite crystals, but never occur together on the same specimen. Gebhard has also reported bismuthinite.

Pasto Bueno and Mundo Nuevo

The Pasto Buena tungsten district in Ancash Department is still one of the most prolific Peruvian localities. It has long been famous for hubnerite, but the most recently found hubnerite crystals have been, in general, smaller than those of the past: they range up to 5 cm, usually as loose singles broken off from quartz druses. Doubly terminated hubnerite crystals from Pasta Buena are very rare. In 1999 there was a find of beautiful matrix specimens with transparent, bright red, platy hubnerite crystals to 2 cm growing on quartz, with colorless fluorite cubes, tetrahedrite, and transparent orange sphalerite crystals to 1 cm resembling scheelite. In 2001, black hubnerite crystals on quartz were found, the largest measuring 6 x 12 cm. Nice orange scheelite pseudo-octahedrons to 1 cm on druses of smoky quartz with greenish muscovite were relatively common a few years ago. Complex, brownish yellow sphalerite crystals to 2 cm, found in January 2003, were mislabeled as "scheelite" in Peru. The difference in fluore scence is diagnostic; the sphalerite shows only weak orange fluorescence on the surface, whereas scheelite typically fluoresces a bright blue-white.

Older specimens of rhodochrosite from Pasto Bueno are among the world's best, but large rhodochrosite crystals have not been found recently--only simple, pink rhombohedrons to 1 cm growing on drusy quartz. Many larger quartz crystals from Pasto Bueno have arsenopyrite, pyrite or chlorite inclusions, and flattened Japan-law twins of quartz measuring 1 or 2 cm have sometimes been collected. Pasto Bueno is also the source of the best recent fluorite specimens from Peru, in pale green to violet crystals reaching almost 10 cm. Nice emerald-green fluorite octahedrons on large quartz crystals (up to 12 x 30 cm!) appeared at the end of 2002. A specimen with pale yellow to colorless crystals of euclase to 1 cm on pink mica and fluorite is in the collection of Art Soregaroli.

The Mundo Nuevo mine near Pasto Bueno yielded several finds of excellent Japan-law twinned quartz in 1998 and 1999. The specimens are very distinctive, in that the milky quartz crystals are long-prismatic and not flattened. In some cases the crystals are doubly terminated, and there are even multiple Japan-law twins, with two crystals growing in parallel from the longer central crystal; large specimens commonly contain several Japan-law twins.

Large tennantite (X-ray verified) crystals to 5 cm were found in 2002, some of them partially covered by green scorodite. Tennantite occurs together with striated pyrite cubes up to 7 cm. Both grow on quartz, and some pyrite crystals are "pierced" by a long quartz crystal. Excellent hubnerite specimens of the same type as illustrated (Fig. 30) in Crowley et al. (1997) were found in 2002. They are dark red and up to 4 cm long, growing on quartz crystal druses.

A roadcut near Mundo Nuevo yielded interesting specimens at the end of 2002. They are druses of small quartz crystals up to about 2 cm long, with small doubly terminated amethyst crystals up to 5 mm growing on the points.

Raura

The Raura district, northeast of Lima in Lima Department, is known for producing Peru's best stibnite. Good groups of very lustrous stibnite crystals to 3 cm long and 4 mm wide, terminated by a low pyramid, were found in 1999, but unfortunately almost all of them were damaged during collecting. Loose, colorless to violet hexagonal crystals to 7 cm were offered as apatite in Lima in 1997, but X-ray analysis has shown them to be aragonite. We purchased a very unusual specimen in December 2002: a matrix encrustation of transparent, violet aragonite crystals up to 3 cm. Each crystal has a hexagonal cross-section, but the termination is "tooth-like," with three individual small crystal points.

Pachapaqui

The Pachapaqui ore district continues to be a source of good bournonite specimens, and of needle-like, slightly bulging arsenopyrite crystals to 1.5 cm long. Bournonite is quite common, and cogwheel-shaped crystals to 3 cm, etched from quartz using hydrofluoric acid, were found in 2001 and 2002. Pink manganoan calcite in crystals and stalactitic aggregates is still found at Pachapaqui, and scepter crystals of quartz are common. Matrix encrustations of colorless fluorite cubes up to 1 cm appeared in 2002. The rhodonite from this locality is much inferior to the rhodonite of Chiurucu, but occasionally it harbors small yellow tetrahedrons of helvite to 2 mm (large ones exist but are extremely rare).

In 1997 the Arabia mine in the Pachapaqui district produced some nice druses of yellow manganaxinite crystals to 5 mm growing on massive rhodonite. Pale yellow dodecahedrons of spessartine to about 1 mm and black veins of alabandite are commonly found on these specimens.

Fine tetrahedrite specimens, with very lustrous, simple tetrahedral crystals to 2 cm associated with sphalerite, were found in August 2001. In the same year, some very interesting specimens were unearthed, showing small tetrahedrite crystals in parallel growth, having formed epitactically on chalcopyrite crystals to about 3 cm; but all of the chalcopyrite had been replaced by pyrite, so that these specimens represent an epitaxy over what is now a pseudomorph. Crowley et al. (1997) mention similar specimens, but incorrectly regard them to be pyrite pseudomorphs after tetrahedrite: we found small grains of relict chalcopyrite occasionally present in the cores of these crystals.

Pucarrajo

The small Pucarrajo mine was assigned to the Pachapaqui district by Crowley et al. (1997), but is actually in a pass halfway between Pachapaqui and Huanzala, and is owned by a different company. During the past few years it has produced many excellent specimens, although these are often mixed in with the more common Huanzala material. In 2000, the Pucarrajo mine yielded what are probably Peru's best pyrrhotite specimens, with sharp, platy pyrrhotite crystals to 5 cm associated with chalcopyrite and black sphalerite crystals on quartz. The pyrrhotite is fresh, and small pyrite cubes line the edges of the pyrrhotite crystals. Clusters of nice chalcopyrite crystals to 4 cm were also found in 2000, including some unusual flattened twins resembling Stars of David. Arsenopyrite is common as silvery white, blocky crystals to about 2 cm, usually with lustrous black sphalerite. Orange scheelite bibyramids to 8 mm associated with arsenopyrite were found in 2001. In a very few specimens, meneghinite occurs in striated c rystals to 1.2 cm-probably the world's best for the species. The most recent unusual find from Pucarrajo, coming at the end of 2002, was boulangerite as long needles up to about 3 cm, forming a felt-like vein on calcite. Its identity was confirmed by X-ray diffraction analysis.

Huanzala

The Huanzala mine in Huanuco Department is famous for producing the best pyrite specimens in the world. Pyrite is still found here in large quantity, but no huge crystals have been seen recently; some highly lustrous octahedral pyrite crystals to about 3 cm, with white barite, are very similar to older specimens from Quiruvilca. Nice pyrite pseudomorphs after hexagonal pyrrhotite plates with black sphalerite have also been found very recently. A very few specimens with black, tapered crystals of cronstedtite to 1.5 cm on pyrite crystals have also been found.

Newly collected "tetrahedrite" specimens were found by X-ray analysis to be tennantite; the crystals are simple tetrahedrons with slightly curved faces to about 1.5 cm. In 2001, very nice, lustrous tennantite (X-ray verified) was found growing on pyrite; unlike the similar, and more common, tetrahedrites from Casapalca, these crystals are simple tetrahedrons to about 3 cm.

In 1998 there was an extraordinary find of wurtzite in the Huanzala mine. The dark brown crystals, with diameters to 1 cm, show a typical hexagonal-pyramidal shape, and grow in clusters with nice white tabular barite and lustrous galena, the last species sometimes spinel-law twinned. Excellent boulangerite specimens with acicular crystals up to 4 cm long were found a few years ago. A gemmy crystal of sellaite 2.1 cm long from the Huanzala mine was described by Moore (1998). There have been no new finds of the famous pink octahedral fluorite from Huanzala, hut specimens of small purple fluorite crystals are common; sometimes they completely cover matrixes to over 10 x 20 cm.

An extremely unusual Huanzala mine specimen owned by Art Soregaroli was pictured on page 130 of the March--April 1998 issue of Mineralogical Record. A gemmy 2.1-cm sellaite crystal on a matrix of quartz, jalpaite, pyrite crystals and chalcopyrite crystals is accompanied by, and partially encloses, native copper wires (identification by E. E. Foord).

Chiurucu

The small Chiurucu mine (not prospect; see Crowley et al., 1997), is famous for having produced some of the world's best rhodonite specimens in 1989 and 1990, and several very nice specimens were found again in the summer and autumn of 1998. They are comparable in size to the best of the older specimens, but their color is generally paler. The mine was reopened in 2001, and there is a good possibility that further finds will be made there.

A quarry near Chiurucu produced a large quantity of beautiful quartz specimens in 2002. The crystals are up to about 15 cm long and 4 cm wide, and all are heavily striated perpendicular to the c-axis. Many of them contain eye-visible inclusions of galena and sphalerite, sometimes in the form of phantoms.

Uchucchacua

Uchucchacua in Lima Department is the fifth largest silver mine in the world, producing 221 tons of silver in 1999. The mine is famous for excellent rhodochrosite in dark red, translucent to gemmy crystals showing complex combinations of scalenohedral and rhombohedral forms. The rhodochrosite crystals grow on a very hard gray to black skarn matrix, with black amorphous neotocite and in some cases with small, colorless quartz or fluorite crystals. The average size of the rhodochrosite crystals is about 1 cm, but exceptionally they reach 4 cm; the authors saw one 8-cm rhombohedron which is very dark (almost black) and damaged. A very strange rhodochrosite specimen, purchased in Lima in 1998, shows transparent scepter-shaped scalenohedral crystals to 1 cm growing on thin, opaque prisms of an earlier generation of rhodochrosite.

Uchucchacua is also famous for its silver minerals. Proustite, for example, is still quite commonly found there. Acanthite (paramorphic after argentite) has been known for some time in crystals to about 1 cm, but in 2000 the mine produced a few sharp, lustrous acanthite crystals to 3 cm, some of them on a matrix of pale-colored rhodochrosite. This acanthite is accompanied by arsenpolybasite (identified by X-ray and chemical analyses) in massive form and as lustrous hexagonal crystals to almost 5 cm. Some arsenpolybasite crystals grow also on large masses of proustite. Splendid white native silver wires to at least 20 cm long were found in the Uchucchacua mine in the spring of 2001, but no silver specimens have been found at Uchucchacua since then. The silver wires are generally very thin and highly lustrous, but beware: some of the wires have been glued onto matrix by the locals.

A beautiful fluorite specimen was found at Uchucchacua in 2001: a group of colorless cubes to 3 cm with small, red proustite crystal inclusions.

Milpo and Atacocha

The Milpo and Atacocha mines in the Atacocha district, Pasco Department, are mentioned only briefly by Crowley et al, (1997), without providing descriptions of any minerals except for the orpiment from Atacocha, of which no recently mined specimens are known. However, these two mines have been among the most specimen-prolific mines in Peru during recent years. Most of the Peruvian dealers who go to the area buy specimens from both the Milpo and Atacocha mines at the same time, and thus are often unsure which mine a given specimen came from, although it seems that during 2000 and 2001 the Milpo mine produced the more interesting material, particularly kutnohorite, amethyst and boumonite.

Highly lustrous bournonite crystals to 1 cm are common from Milpo and Atacocha, and resemble the better-known pieces from Quiruvilca and Pachapaqui. Usually they are tabular single crystals, but striated cogwheel-type twins have also been found. Tetrahedrite from Milpo generally occurs in small crystals; good specimens are very rare, but can be very aesthetic. The best contain highly lustrous black tetrahedrite crystals to 3 cm, each a parallel growth aggregate of smaller crystals. Massive galena is very common, but we have seen no interesting galena crystals except for a few flattened crystals epitactically oriented on striated pyrite cubes. Pyrite specimens from Milpo have been common for several years; the largest good specimen we observed weighs about 25 kg. The pyrite crystals are almost always simple cubes to 5 cm; bigger crystals are very rare.

Fluorite from these mines can be violet, colorless or bluish, and is commonly transparent. The crystals, averaging i or 2 cm on edge, are combinations of cube and dodecahedron forms; a few specimens with larger, octahedral fluorite crystals sprinkled with pyrite crystals were also found. Yellow blocky barite crystals up to 1.5 cm, sometimes growing on quartz crystals, were found in Atacocha in 2002.

Quartz is the most common species from Milpo and Atacocha, and is easily distinguishable from the quartz found at other Peruvian mines. Quartz crystals on many of these specimens have a slightly barrel-shaped form; small scepter crystals have also been observed. Crystals of pseudo-pyramidal habit--i.e. two rhombohedrons, without prism faces simulating a hexagonal bipyramid--reach up to about 3 cm, and groups of these crystals reach more than 20 cm across; they are very lustrous, and some have reddish phantoms. Amethyst, which is very rare in most other Peruvian mines, is quite common at Milpo. Pale-colored amethyst forms crystals to i cm in druses, rarely over rhombohedrons of calcite. Some amethyst crystals have a slightly rounded, pyramidal shape, and reach 3 x 5 cm. A few pieces collected in August 2001 show a very strange habit: pale-colored crystals to 3 cm wide and 5 cm long, the crystals have hollowed-out terminations resembling volcanic craters, complete with small peaks in their centers. Orange botr yoidal aggregates of chalcedony up to about 5 mm in diameter are one of the most interesting recent finds from Milpo, and are probably unique for Peru. They were observed on a very few pieces of crystallized quartz, and were called rhodochrosite by local dealers. But colorless to brownish chalcedony is common as a coating or botryoidal encrustation on many quartz crystals.

Calcite is common in both the Milpo and Atacocha mines, as white, yellowish or reddish crystals occurring in several generations and reaching several centimeters in length. Crystals of earlier generations are opaque, while later crystals are translucent to transparent. A few specimens of calcite twins encrusted by rhodochrosite were found in the Atacocha mine in 2001. Pink crusts covering calcite and kutnohorite from both mines were identified by X-ray analysis as rhodochrosite. These rhodochrosite crusts range from extremely thin to about 3 mm thick. The Atacocha mine has also produced rod-like rhodochrosite formations on matrix. Pale single rhodochrosite rhombohedrons up to about 8 cm covered by calcite or quartz appeared in 2002. The Milpo mine also has produced several lots of nice siderite specimens. Some siderite crystals are lens-shaped, while others are pale brown rhombohedrons to about i cm.

The biggest surprise during a study of recent specimens was the X-ray analytical determination of kutnohorite from the Milpo mine. The kutnohorite crystals are simple, white to beige rhombohedrons growing on quartz and pyrite; in some cases they are covered by a crust of younger, pink rhodochrosite or by calcite crystals. Reaching sizes of more than 10 cm, these are probably the largest and most aesthetic crystals of kutnohorite in the world! They are easily distinguishable from similar-looking calcite crystals by their much weaker solubility in dilute hydrochloric acid.

Alimon and Huaron

Alimon is mentioned as one of the Huaron group of mines in Crowley et al. (1997), but is in fact an independent mine on the other side of a mountain. It has a different owner than the Huaron mines and, according to the miners, it was producing much more ore than Huaron during our visit in August 2001. Huaron has thus far produced only small numbers of specimens, most notably clusters of small chalcopyrite crystals on massive calcite and rhodochrosite, and occasional groups of small rhodochrosite crystals. But in 2002, Huaron produced a large number of specimens of beautiful thick quartz crystals up to 2 cm long growing on small rhodocbrosite aggregates. In some cases the quartz is accompanied by tetrahedrite crystals to 1 cm or by sphalerite crystals completely covered by a chalcopyrite crust. At the end of 2002 there was a very unusual find of rhodochrosite pseudomorphs after barite (2), some of which are penmorphs (hollow molds); these reach about 6 cm. Growing on them are hemispheres of black sphalerite, and sometimes even red pyrargyrite crystals to 2 mm.

The Alimon mine is still producing very aesthetic specimens of pyrite, sphalerite and chalcopyrite growing amid beds of needle quartz crystals (very rarely Japan-law twinned). Surprisingly, there was a find in 2000 of colorless fluorite octahedrons; the biggest single crystal is 19 cm on edge and weighs 3.5 kg! In 2001, the Alimon mine yielded small druses of tiny stibnite needles growing on quartz.

Carhuacayan

This mine, closed at the time of visits by Crowley et al. (1997), is producing again. Specimens of sphalerite, pyrite, galena and bournonite seen in Lima in 2002 are very similar to old ones from the locality.

Morococha and Manuelita

In 1998 the Morococha mines produced a few very dark green, almost black, vivianite crystals to 2 cm, some with small black sphalerite crystals, on massive pyrite. In 2001 some unusual quartz crystals to 20 cm long with parquet surfaces were found. A limited number of unusual nubnerite specimens came from Morococha in May 2002: groups of black platy crystals up to 1.5 cm long, 3 mm wide, but only about 1 mm thick. They show red only when very strongly backlit. The crystals grow on groups of large pyrite crystals, with nearly black sphalerite crystals to 5 mm. In January 2003 there was a unique find of a few gemmy gypsum crystals up to about 10 cm long, which contain inclusions of pale pink rhodochrosite and sphalerite. Nice pink rhodochrosite rhombohedrons up to 7 mm on black sphalerite were found sparsely.

The Manuelita mine, about 2 km from Morococha, along the road to La Oroya, has been producing beautiful rhodochrosite crystal specimens for several years. They look distinctly different from rhodochrosite from other Peruvian sources: simple, pink-red rhombohedrons to 1 cm in groups to 20 cm. Some of the rhombohedrons reach 3 cm, but these larger ones are very palecolored and not attractive. Massive banded rhodochrosite from veins in the Manuelita mine is often tumble-polished, and the finished stones strongly resemble the famous rhodochrosite from Mina Capillitas in Argentina.

Casapalca

The most recent major find of excellent tetrahedrite crystals at Casapalca was made during the summer of 1998, and production of specimens continued sporadically until summer 1999. Thousands of specimens were extracted, but only a minute percentage of them were recovered undamaged.

The products of this large find can be divided into three major types. In the most common type, simple tetrahedrons of tetrabedrite to 3 cm, exceptionally to 7 cm, rest on drusy quartz. These crystals are very often found covered by white calcite, which Peruvian dealers dissolve away with hydrochloric acid; these acid-treated specimens unfortunately have much lower luster than the rare untreated ones. The second specimen type, much rarer and more beautiful, consists of tetrahedrite crystals associated with highly lustrous black sphalerite crystals. The latter species is often pseudo-octahedral in form, and grows in parallel groups; the tetrahedrite crystals show combinations of the positive and negative tetrahedrons with the negative faces selectively coated by a very thin crust of chalcopyrite. The third and rarest assemblage consists of gray tetrahedrite crystals with dark brown, extremely lustrous sphalerite crystals, both covered by bournonite crystals to 5 mm. The bournonites are very complex and rounded, not the more common cogwheel twins. Some of the tetrahedrites have been naturally corroded, and are irregularly pitted, the holes overgrown by very small calcite scalenohedrons.

A few huge tetrahedrite crystals to 13 cm on edge have been found at Casapalca; these grow on pyrite and do not have a high luster. Some nice specimens of gray chalcopyrite crystals to 3 cm with coatings of tetrahedrite, growing on quartz and calcite crystals, were also recovered. A few druses of cogwheel bouruonite crystals to 1 cm on quartz appeared again in 2002.

Casapalca has also yielded some interesting specimens of quartz, brown gypsum, and calcite (including pink scalenohedrons of manganoan calcite). Very unusual specimens of arborescent native copper, probably also from Casapalca, appeared in 2001; some have associated white gypsum crystals.

San Genaro

The San Genaro mine in the Castrovirreyna district, Huancavelica Department, is still the most prolific locality in Peru for silver minerals. It yields primarily small specimens of crystallized pyrargyrite, with rarer miargyrite (in nearly black, lens-shaped crystals), polybasite (in hexagonal plates), stephanite and freibergite (both in complex, gray, highly lustrous crystals). The best freibergite (X-ray verified) occurs as very complex, rounded crystals to 1.5 cm, on barite with pyrargyrite and rarely with bournonite crystals; these specimens were found in 2001. Interesting columnar crystals of realgar to 1.5 cm, strongly resembling recently found crystals from Baia Sprie, Romania, were found in 2001; the realgar has formed on tetrahedrite and sphalerite.

The new, very rare species baumstarkite, [AgSbS.sub.2], a polymorph of miargyrite, was described recently from San Genaro by Effenberger et al. (2002); for a long time this material was thought to be aramayoite. Baumstarkite forms black crystals to about 3 mm (commonly twinned) on miargyrite, as well as cleavages resembling wolframite. There have probably been no new finds of the species, but it can be seen on older specimens.

Nice clusters of columnar to rounded 1.5-cm pyrargyrite crystals have been found sporadically at the San Genaro mine. Surprisingly, some "pyrargyrite" specimens found in 1999 were determined by X-ray analysis to be proustite. These crystals reach 1 cm, and have flatter, shinier surfaces than the pyrargyrite from other recent finds. Native silver from San Genaro is usually found as small wires, but in the summer of 2000 some herringbone-style aggregates resembling those from Batopilas, Mexico were discovered. A fantastic silver specimen of this type, about 15 cm tall, was exhibited in February 2001 at the Tucson Show.

Julcani

The Julcani mine continues to be a very prolific locality. Very good crystals of enargite to 7 cm, similar to old specimens from Quiruvilca, were found in 1999; they occur on platy white barite crystals which reach more than 10 cm. Very rarely, the enargite forms star-shaped twins. A very interesting find in the summer of 1999 produced many sharp pseudomorphs of tennantite after enargite to more than 7 cm long. The larger crystals may be hollow, or may contain relict enargite in their centers. A few groups of pseudomorphic crystals to 1.5 cm are covered by fine-grained pyrite; these are composed of an intermediate member of the tetrahedrite-tennantite series. Complex, rounded, highly lustrous gray crystals to 1.5 cm have been identified as tetrahedrite.

Julcani has also recently produced nice stalactites of pyrite and of marcasite, and some bournonite crystals as well. Nice pyrite octahedrons up to about 5 cm on matrix appeared in 2002. Very rare, complex intergrowths of acicular bismuth sulfosalt crystals on barite are known from the past, and a few excellent specimens of krupkaite (verified by X-ray and microprobe analysis), with needles to 4 mm, were found in 1999. Very similar specimens found at earlier times at Julcani have been identified as bismuthinite and/or boulangerite.

In December 2002 specimens of black wolframite crystals up to about 1 cm appeared, accompanied by clusters of tiny gold crystals; these clusters reach about 3 mm. They were originally covered by calcite which was etched off.

Pampa San Jose

Although Peru is among the world's leading gold producing countries, collector-quality Peruvian gold specimens are almost unknown. However, in 2000 a few attractive specimens of wire gold appeared, purportedly from Pampa San Jose, Carolita, Huancay. The specimens consist of massive vein quartz and abundant limonite, with gold wires to about 1 cm.

Laguna da Salinas

This salt deposit near Arequipa, currently being exploited, has produced some interesting borates, including spherical aggregates of inyoite crystals to 15 cm and crystallized ulexite.

Ica region

Good mineral specimens from southern Peru were almost unknown in the past, but this changed with some significant discoveries in the late 1990's. Nice brown ferro-axinite in sharp crystals and groups to about 7 cm was found in Molletambo, 40 km east-southeast of Ica. Rarely the ferro-axinite is accompanied by prehnite and black tourmaline. Gray apatite crystals to 7 cm have been found at the nearby locality of Espinal (Moore, 1998); some good epidote specimens appear to have come from the same source. A much less important epidote locality is the Paracas quarry near Huaytara, on the border of Ica and Huancavelica departments. Although the epidote crystals from this occurrence are not nearly as fine as those from Pampa Blanca, they are made more interesting by their association with ferro-axinite.

The region between Pisco and Ica apparently contains more localities for interesting vein quartz. Several habits of quartz from this area have appeared in Lima during the past few years. In February 1999 the authors saw terminated quartz crystals to about 30 cm long, reportedly from an unnamed prospect near Pisco; they resemble specimens from Pampa Blanca Lustrous black schorl crystals to 2 cm on feldspar matrix were mentioned by Moore (1998); their locality was given as Chacoya, Castrovirreyna Province, Huancavelica Department (east of Pisco). An unknown locality in the Ica region produced beautiful orange calcite scalenohedrons to several centimeters long. This calcite is transparent, but has an opaque crust; some crystals with artificially polished surfaces have been sold.

Pampa Blanca and Ullpac

The first Japan-law twinned quartz specimens from southern Peru appeared on the market around 1997. Secretive local suppliers have given various locality names, but the source is the Rosario Mabel claim near Pampa Blanca in Castrovirreyna Province, Huancavelica Departtnent. Between 1995 and 1998 this claim also produced huge quantities of fine epidote specimens. In 1999 the claim was sold to a new owner, G. Russo, who renamed it "Flor de Peru II." The occurrence is at a contact between granite and carbonate rocks, where abundant andradite garnet, rarely in crystals to 2 cm, has been found with epidote. The epidote characteristically forms sprays of thin needles up to about 10 cm long; thick terminated crystals are quite rare. Japan-law twinned quartz here is rarer than at Ullpac Mountain (also written as Ullupac; see below); the crystals are similar in habit to the Ullpac specimens, but are transparent and thus much more attractive, The biggest specimen to reach the Lima market in 2001 weighs about 200 kg and contains at least 10 Japan-law twins, each twin about 10 cm across. A huge 49-cm twin was found at Pampa Blanca in 2002. Rarely, calcite crystals occur on the quartz twins.

Probably the world's most productive locality for Japan-law twinned quartz at present is the "Flor de Peru r' claim at Ullpac Mountain, situated about 3 km north of Pampa Blanca; this abandoned copper (7) mine (which was called the Tentadora mine when it was active) began to produce specimens in 1999. The crystals come from simple quartz veins and are rarely accompanied by epidote, green platy vesuvianite, small scheelite crystals and pale amethyst. Quartz here forms crystals to about 20 cm long. Japan-law twins are very common, averaging about 5 cm, occasionally reaching 10 cm. The twins are almost always flattened, and range in shape from the typical "V" through heart-shaped to very rare "closed squares." The twins are usually accompanied by untwinned quartz crystals, but one part of the vein produced a limited number of groups to more than 30 cm in size, composed entirely of large Japan-law twins. Unfortunately, Ullpac quartz twins are usually rendered milky by a thin crust of younger, white quartz. Very rarely the twins show green chiorite phantoms or are terminated by amethyst scepters.

Las Salinas

The Las Salinas halite mine near Otume village south of Pisco (not to be confused with Laguna de Salinas near Arequipa) has produced very aesthetic clusters of golden gypsum crystals during the last two years. The crystals reach about 7 cm and are commonly twinned on {l00}. The only associated mineral is halite in colorless cubes to about 5 cm. The most recently found gypsum specimens are among the most beautiful known.

Lily mine

Secondary minerals are rare in Peru, and thus the discovery of very beautifully crystallized secondary copper minerals in 1998 was very surprising. The locality is the Lily mine, about 40 km east of Pisco and about 200 km south of Lima. Originally the material was called brochantite, but X-ray analysis has shown it to consist primarily of atacainite. The most beautiful specimens show bright green, flattened prismatic crystals to several millimeters completely enclosed in younger gypsum crystals; an example is shown on the cover of the May--June 2000 issue of the Mineralogical Record. Much rarer are blocky, almost pseudocubic, greenish black crystals of paratacamite from the Lily mine. These can reach 1.5 cm and are surely among the world's finest examples of the species. Also, malachite forms bright green radial crystal aggregates, in some cases covered by younger quartz or gypsum; the aggregates can resemble paratacamite. Gypsum crystals from the Lily mine commonly show inclusions of pale blue, amorphous ch rysocolla. Nice blue-green lapidary material, referred to as "gem silica," consists of chalcedony stained by chrysocolla inclusions (Hyrsl, 2001).

Acari

The Acari mine exploits what is probably a porphyry-copper orebody near Nazca in Arequipa Department. For at least two decades it has produced large quantities of lapidary-grade chrysocolla (called "turquesa" in Peru), as well as transparent blue opal (described in the trade as "Andean opal") which is colored by chrysocolla inclusions. Mixtures of opal, chalcedony and chrysocolla in varying proportions, with varying refractive indices and densities, have been described by Hyrsl (2001). The same locality is also producing pink opal which contains a significant amount of palygorskite.

Unknown localities

In 2001, some very interesting amethyst specimens were found at a locality first given as near Cuzco, later given as near Nazca, not far from Ica. The best specimens show amethyst scepter crystals to about 7 cm.

An unknown locality in central Peru produced a few specimens of faden quartz in 2001. The slightly twisted crystals are about 5 cm long and of mediocre quality.

In 1998 a few very large, transparent, orange scheelite crystals appeared at the Tucson Show, and later they were cut into huge faceted stones to 266.68 carats. The loose crystals closely resemble those from China. We were told in Lima that they come from the Turmalina mine in Piura Department in far northern Peru, but this attribution needs confirmation.

Acknowledgments

We warmly thank Rainer Bode, publisher of Mineralien Welt, for granting us permission to publish this composite article, based on our various earlier reports, and we thank Tom Moore and Wendell Wilson for much help with editing. We thank Art Soregaroli for providing information about Peruvian specimens in his collection. Many thanks also to all our friends in Peru for furnishing much information and showing us many new specimens.

References

CROWLEY, J. A., CURRIER, R. H., and SZENICS, T. (1997) Mines and minerals of Peru. Mineralogical Record, 28 (4), 1-98.

EFFENBERGER, H., PAAR, W. H., TOPA, D., GRIDDLE, A. I., and FLECK, M. (2002). The new mineral baumstarkite and a structural reinvestigation of aramayoite and miargyrite. American Mineralogist, 87, 5-6, 753-764.

GEBHARD, G. and SCHLUTER, J. (1998) Die weltbesten Kristalle von Famatinit und Luzonit. Lapis, 23, 9, 35-37.

HYRSL, J. (1999) Em neuer Tetraedrit-Fund in Casapalca, Peru. Mineralien Welt, 10, 4, 56, 57.

HYRSL, J. (2001) Gemstones of Peru. Journal of Gemology, 27, 6, 328-334.

HYRSL, J. and ROSALES, Z. (2000) Neue Mineralienfunde aus Peru. Mineralien Welt, 11, 5, 23-31.

HYRSL, J., and PETROY, A. (2001) Quarz-Zwillinge nach dem Japaner-Gesetz aus Peru und Bolivien. Mineralien Welt, 12, 4, 46-49.

HYRSL, J., PETROV, A., and ROSALES, Z. (2001) Einigeneue Mineralienfunde aus Peru und Bolivien. Mineralien Welt, 12, 4, 62-64.

HYRSL, J. and ROSALES, Z. (2002) Die Bergwerke von Milpo und Atacocha--ein neue Quelle schoner Mineralien in Peru. Mineralien Welt, 13, 3, 50-55.

MOORE, T. (1998) What's new in minerals: Denver show 1997. Mineralogical Record, 29 (2), 125-133.
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Author:Hyrsl, Jaroslav; Rosales, Zolina
Publication:The Mineralogical Record
Geographic Code:3PERU
Date:May 1, 2003
Words:5768
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