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THE ALTO LIGONHA PEGMATITES MOZAMBIQUE.

The Alto Ligonha pegmatite field was an important producer of fine crystallized pegmatite minerals during the 1930's to 1970's. Though it has been less productive in the 1980's and 1990's, it is currently enjoying a revival phase. Specimens continue to be produced, and superb examples of elbaite, beryl, stibiotantalite, ferrotantalite, microlite, topaz, zircon and other species are preserved in museums and private collections worldwide.

INTRODUCTION

Alto Ligonha (pronounced "Lig-own'-yah") is the name of an administrative post founded during the period of pacification of the tribes of northeastern Mozambique, which ended around 1895. The name refers to the upper ("Alto") course of the Ligonha River.

Pegmatites of varied mineralization occur over a broad area, the heaviest concentrations being near the town of Alto Ligonha. There seems to be some confusion as to the actual extent of the Alto Ligonha district proper, some believing that it must refer primarily to the first and most important mine in the district, the Muiane. For the purposes of this article, however, we will follow the broader usage of most authors (DeKun, 1965; DSGM, 1974; etc.) and include the entirety of what might be called the northern Mozambique pegmatite province, that is, an area within approximately a 200-km radius of Alto Ligonha. This encompasses almost every pegmatite in Mozambique except those in or near the Mozambican panhandle (e.g., Tete), which are more closely related to the geology of nearby Malawi, Zambia and Zimbabwe.

The area is within the East African Monsoon Belt, at an average altitude of about 400 meters; temperatures are moderately hot in the summer and pleasantly cool in winter. There are two seasons: the cool, dry season (April to October) when the Monsoon blows eastward, and the rainy season (November to March) when the Monsoon reverses itself and blows across the Indian Ocean from India to Mozambique. Rainfall averages 100 to 120 cm per year.

Access to the Alto Ligonha area is either (1) by air to Nampula--whose airport is served regularly by Mozambique Airlines--and from there by car to Murrupula and thence to Muiane, or (2) by air to Quelimane, then by rail or car to Mocuba, and from there onward to Alto Molocue, Alto Ligonha Post, and Muiane. The former route is the preferable one.

The best time of the year to visit Alto Ligonha is June to October, after the rainy season has ended and the roads have been repaired. For travel during the rainy season, a vehicle with four-wheel drive is a must, and information on the condition of roads and bridges should be obtained from local authorities before heading out.

Mineralogists and mineral collectors visiting the area should always check in beforehand with the Geological Survey of Mozambique headquarters in Maputo. They are very helpful in explaining regulations that apply to taking mineral specimens out of the country, and can advise on the best routes to the mines.

Although Alto Ligonha has a pleasant climate and is free of sleeping sickness, it must be remembered that since the country gained its independence from Portugal in 1975, malaria and other tropical diseases which had been nearly eradicated have come back in more virulent forms. While hunting laws prior to 1975 protected the native animals, widespread destruction of local species occurred thereafter. As a result, the proliferation of man-eaters among the population of big cats has become alarming. In consideration of these dangers, visitors should take antimalarial medicines (not generally available in Mozambique), should avoid being bitten by mosquitoes, and should assume that no water is safe to drink until it has been boiled. No stream is safe to wade in due to the possible presence of crocodiles and the certainty that it will be infected with bilharzia, the carrier of schistosomiasis. As for safety from wild animals, the best protection is to avoid going into the bush without a local resident as guide, an d to follow his advice implicitly.

HISTORY

Toward the end of the 19th century, conflicts erupted between the Portuguese (who controlled the ports) and local potentates allied with Indian and Arabian slave traders. The slavers were defeated, opening up the interior for the first time to Europeans (who traded European goods in return for gold dust). During the first World War, the German East African Army marched through Mozambique, engaging British, Portuguese and South African forces at the Alto Molocue, Alto Ligonha, and Mamala military posts which were under Allied control.

Attached to the Portuguese Army units that took the brunt of the German offensive were convicts serving sentences for crimes committed in Portugal. Many of these convicts saw their sentences pardoned for acts of bravery in combat; after the end of hostilities they settled down as farmers, traders and prospectors. Alluvial gold and gem-grade tourmaline were first produced as a result of their work in the area.

Rubellite (red to pink tourmaline) was the first gemstone to be found in the Alto Ligonha area. It occurred in the eluvial rubble on the north slope of the Muiane pegmatite, where crystals were dug Out by the first prospectors. One of those prospectors (so the story goes) showed the crystals to the captain of a German merchant ship docked at Mozambique Island. The captain correctly identified the specimens, concluded that they would bring a good price in Germany, and purchased the lot. A steady trade developed through individuals in the German merchant marine which lasted until the outbreak of World War II.

In 1936 one of us (MBD) saw a lot of those early, prospector-dug stones which someone had put away on Mozambique Island. There were nearly two dozen prismatic crystals of various sizes from about 1 x 2 cm up to 4 x 10 cm. All were perfectly gemmy and flawless, although the terminations (typically fracture-filled) had been cobbed off. All were a deep pink, except for the rare wine-red examples.

Pegmatites in the Alto Ligonha area were first actively mined around 1926, and continued in operation for several decades thereafter. The district was under the administration of the Nyasa Company until 1929, when it was taken over by the government. The best-known pegmatite is probably still the Muiane, which was operated by Empresa Miniera do Alto Ligonha, and which has produced many collector specimens now in museums.

In 1930 a report on the mineral potential of northern Mozambique was prepared for the Mozambique Department of Mines by Antonio J. Freitas, a distinguished mining engineer and first director of the Department. During the 1940's extensive prospecting [1] by the Mines and Geology Department located alluvial gold deposits in the valleys of the Cocone, Metuisse and Namirroe Rivers. It was also during this time that the first geological map of the area, on a scale of 1:250,000, was completed by Alexandre Borges and Arthur F. Nunes. In 1949 the American mining engineer and mineral collector Mark Chance Bandy (1900-1963) visited the Alto Ligonha district for several days and was impressed by the superb quality of crystals being found there. His report was published in 1951.

A geological reconnaissance by the American firm E. J. Longyear Company was conducted under contract to the Portuguese government during 1953 and 1954, while an investigation of economic potential was done by R. W. Hutchinson and R. J. Claus for the Union Carbide and Carbon Corporation. From 1954 to 1962 additional (unpublished) reports were produced by M. Bettencourt Dias, G. Myers, Lopes da Silva, J. Sabot, E. Mendelson, J. Browne and Alexandre Borges. An article by Bettencourt Dias on the pegmatites of Alto Ligonha was published in 1961 as Bulletin no. 27 of the Geology and Mines Service of Mozambique. In 1962, Fernando Freitas, a mining engineer, published an explanatory notice to Geological Sheet Sul-D-37/U, Alto Ligonha-Murrupula, in Bulletin no. 28 of the Geology and Mines Service, including geologic maps of the pegmatites then in operation which had been prepared by himself and Bettencourt Dias. Since that time, many mineralogical reports on individual species have been published by many authors incl uding Th. G. Sahama, M. Lehtinen, O. von Knorring, J. M. Correia Neves, J. E. Lopes Nunes, E. Saari, R. Quadrado, and others.

In April of 1974 a revolution took place in Portugal, led by Marxist-leaning elements of the military. They handed over independent authority in Mozambique to Russian-trained guerrilla leaders who had tried unsuccessfully for years to gain power there. Immediately the traditional authorities were persecuted; many of the most respected chiefs were hanged, and the Achirima tribe, one of two principal ethnic groups in the Alto Ligonha area, was treated with special brutality. The Achirima were artists, music lovers and intellectuals, and consequently were marked for extermination in a kind of "cultural revolution" similar to that suffered by China.

At the mines, work was suspended daily so that workers could attend political indoctrination sessions. Salaries were raised almost every month but (lacking significant production) were never paid. The production crisis was blamed on the pre-independence staff, who were arrested, tried, given fines too heavy to pay, and assigned jail sentences. The jails, however, were already jammed with noncommunist prisoners and there were no funds made available for feeding them, so many prisoners were simply released.

In order to finance the communist party (called "Frelimo," Frente de Libertacao de Mozambique, which is still in power), workers were encouraged to dig intensively for gem minerals such as tourmaline, aquamarine and emerald. This gem material was then sold by party leaders to Tanzanian black marketeers.

In the 1980's the Central Committee brought in Russian advisors and so-called "mining experts" from Romania and East Germany to improve production and stop illegal sales. Unfortunately the highly paid "experts" were innocent of any real mining or geological knowledge, and the only result was an increase in general starvation among the local population. What few specimens were found were sold on the black market as usual. Eventually the Party became disenchanted with the East European "experts" and expelled them. Some degree of free-market competition was subsequently allowed, and private investors were encouraged to return.

The Mines Department was reorganized and a new discipline was enforced, significantly reducing the level of contraband. The Department was placed in charge of the Alto Ligonha mines, and there is now a limited production of gems and mineral specimens being sold through government-owned shops. The Mines Department is currently said to be very interested in seeing the mines reopened on a larger scale under competent management. Time will tell whether conditions and production will continue to improve, but today the outlook is brighter than it has been in many years.

GEOLOGY

The pegmatite district lies within the Gneiss-Migmatite Complex, a huge area of metamorphic rocks and granitic intrusions of pre-Karoo age. These rocks are part of the Mozambique Belt, which has yielded rich mineral and gem wealth from Mozambique through Kenya and Tanzania. The most important geological units are (1) the regional gneisses, the oldest series, probably of Archaean age; (2) the metasediments, primarily schists, paragneisses and quartzites of varied compositions, probably of Proterozoic age; (3) the granites, consisting of several intrusions which have invaded the metamorphic rocks and emitted pegmatite bodies striking radially outward into the country rock; they are Proterozoic or younger and (4) the basic and ultrabasic dikes which cut across older units.

Pegmatites are quite common throughout the Precambrian rocks of Mozambique. However, with the exception of scattered bodies in the Tete, Niassa, Mocambique and Manica districts, it is in Zambezia that they are most spectacular, not only in number but in size and the wealth and variety of their mineralization. An inventory carried out in an area not especially rich in pegmatites (Gouveia, 1974) revealed over ten pegmatite outcrops per 100 square kilometers, of which 3.4% were economically exploitable.

In the Alto Ligonha area the pegmatites occur in fine-grained gneiss, schist, granulite, migmatite and basic to ultrabasic rocks. In form they range from long and vein-like to egg-shaped, and from vertical to flat horizontal. In size they may be a few tens of meters long and less than 10 meters wide, or up to several kilometers in length. The Muiane pegmatite, perhaps the most important specimen producer, is 400 meters wide and a full kilometer long!

The richest pegmatites have a well-developed concentric zoning, usually with very large quartz cores, and have been subjected to deep albitization. In most of the best deposits, intense kaolinization of the feldspars and abundant lithium mineralization is common. The detailed geochemistry of these pegmatites has yet to be thoroughly studied, but the influence of the host rocks on the composition, and the concentration of tantalum-niobium minerals and gem crystals in zones of albitization and lithium enrichment is conspicuous. Hutchinson and Claus (1956) have observed that pegmatite bodies containing ferrocolumbite, beryl, lepidolite, bismuth and presumably the other accessory minerals of complex pegmatites are restricted to the schists, whereas the pegmatites emplaced in granitic rocks are simple. They also detected a regional zoning in the district based on the presence or absence of lithium minerals.

Cotelo Neiva and Correia Neves (1960) determined the following sequence [2] of crystallization for pegmatite minerals at Alto Ligonha: (Note: not all species are present in every pegmatite.)

(1) Rutite [rightarrow] Zircon [rightarrow] Monazite [rightarrow] Ilmenite [rightarrow] Magnetite [rightarrow] Spessartine [rightarrow] Biotite [rightarrow] Muscovite [rightarrow] Oligoclase [rightarrow] Orthoclase [rightarrow] Quartz

(2) Lepidoite + Quartz

(3) Microcline [rightarrow] Quartz

(4) Monazite + Fluorapatite + Amblygonite + Quartz

(5) Topaz + Lepidolite + Quartz

(6) Albite + Spodumene + Muscovite + Quartz

(7) Tourmaline + Quartz

(8) Beryl + Gadolinite + Quartz

(9) Albite + Lepidolite + Muscovite + Quartz

(10) Ferrotantalite-Ferrocolumbite + Stibiotantalite + Samarskite + Pyrochlore + Thorogummite + Quartz

(11) Albite + Lepidolite + Muscovite + Quartz

(12) Tourmaline + Quartz

(13) Cassiterite + Lepidolite + Muscovite + Quartz

(14) Fluorite

(15) Muscovite + Quartz

(16) Chalcopyrite + Pyrite

(17) Cookeite + Sericite + Quartz

(18) Kaolinite + Montmorillonite + Bismutite + Quartz

The accompanying map of the Alto Ligonha district shows 27 different groups of pegmatites, each of roughly similar mineralization and morphology, all of which were being actively mined as of 1970. Mines that had previously been worked out and closed down (of which MBD himself supervised over 50) are not shown.

Table 1 lists the major mines and the most important mineral species found at each. Comparing the characteristic mineralization of each group of pegmatites to the host rock lithology gives clues which may aid in prospecting for additional deposits. It must be remembered that the hundreds of pegmatite bodies already mined represent only a small fraction of the district's potential. Bandy (1951) wrote:

Due to the vegetation and lateritic soil, the only pegmatites known to date are those with quartz cores that [crop out prominently] or those containing relatively large amounts of mica with shallow cover of soil. So many pegmatites have been found in this way that there has been no need for systematic prospecting. Should modern geophysical prospecting methods be employed, many new pegmatites could be found.

MINERALS

Albite NaAl[Si.sub.3][O.sub.8]

Albite occurs as typical pegmatitic "cleavelandite," glassy white crystal plates up to 15 cm, at the Cavala mine. Attractive clusters with quartz and orthoclase measuring over 75 cm across have been collected there (Bandy, 1951). The cleavelandite habit is also common at other pegmatites, including Muiane, where it shows the forms {010}, {110}, {110}, {101}, {001}, {130} and {130}. Correia Neves and Lopes Nunes (1966 a,b) made a detailed geochemical study of feldspars in the Alto Ligonha district, noting that the Ca-content of albite is very low, as are the K and Rb contents.

Allanite-(Ce) [(Ce,Ca,Y).sub.2][(Al,[Fe.sup.2+],[Fe.sup.3+]).sub.3][(Si[O.sub.4]).s ub.3] (OH)

Allanite is known to occur in at least four different pegmatite groups: the Leonora-Mueterere-Namacala group, the Niesse-Isabela pegmatites, the Guilherme-Comua-Muetia group, and the Ile pegmatite. Associations include betafite, euxenite, monazite and xenotime-(Y) (DSGM, 1974).

Amblygonite (Li,Na)Al(P[O.sub.4])(F,OH)

Amblygonite and other lithium-bearing minerals are reported to occur in seven different pegmatites and pegmatite groups including the Muiane-Naipa group, the Piteia-Nahia-Mirrucue group, the Murropoci-Nuaparra group, the Morrua pegmatite and the Marropino pegmatite (DSGM, 1974).

Andalusite [Al.sub.2]Si[O.sub.5]

Cotelo Neiva and Correia Neves (1960) reported rare, rectangular crystals of andalusite showing {110}, {001}, {011} andat the Muiane mine.

Bermanite [Mn.sup.2+][[Mn.sup.3+].sup.2][([PO.sub.4]).sub.2][(OH).sub.2]*4[H.su b.2]O

Correia Neves and Lopes Nunes (1968) described bermanite, eosphorite, variscite, phosphosiderite, hureaulite, montebrasite, fluorapatite, amblygonite, and triplite from Alto Ligonha pegmatites.

Beryl [Be.sub.3][Al.sub.2][Si.sub.6][O.sub.18]

Beryl at Alto Ligonha occurs mainly in the perthite intermediate zone, in crystals up to 900 kg, and also near the quartz core (Sinkankas, 1988). It is an important ore mineral at many mines in the district, over 100 tons of industrial-grade material having been produced before 1950. Ore beryl was typically an opaque, mottled green color, and crystals commonly exceeded a meter in diameter (Bandy, 1951). In fact, Mitchell (1959) describes one crystal exposed in a quarry wall that measured an astounding 2.44 meters in diameter and extended many meters into the pegmatite. Some of the rose-colored gem crystals can be quite large; Guillemin and Mantienne (1988) describe a crystal fragment weighing 7 kg as being only one-seventh of an original 50-kg crystal. Another rose-colored crystal they noted measured 9 x 25 cm with perfect faces.

Gem-grade beryl was also an important product, much of it hand-cobbed out of larger, partially opaque crystal sections. Roughly 60% of the district's production of gem beryl was aquamarine, and the rest was pink, golden yellow, dark blue, black, colorless, and even (at the Niane and Maria III pegmatites) deep emerald-green (DSGM, 1974; Bancroft, 1984).

Particularly unusual are the black beryls, which at the Muiane pegmatite display a pyramidal 140411 habit. Bettencourt Dias (1961) attributes their color to inclusions; Behier (1957) agreed, suggesting that the crystals are basically aquamarine clouded by manganese oxides. Black beryl has been found also at the Maridge, Naipa, Muhano and Nahora pegmatites. Cotelo Neiva and Correia Neves (1960) described zoned crystals with black cores surrounded by green beryl, or with white to green cores and rims bracketing an intermediate zone of black beryl.

Morphologically most of the better crystals are composed of the pinacoid {000l} plus {1010}, (11211}, {5160}, and {3031}. Beautiful rose-violet crystals are often tabular and gemmy, with {0001}, {1011}, {1121}, {2131}, {3141}, and rarely {1122} and {1.0.1.12} (Sinkankas, 1988). Rose-red to salmon-pink crystals are often very gemmy and tabular with only the c-face being smooth; the numerous other forms present are typically very rough and corroded.

Many fine crystal specimens have been preserved in collections. A sharp, well-formed, 5 x 7.5-cm crystal of non-gem-quality morganite from the Muiane mine is in the Smithsonian collection (Bandy, 1951). Behier (1957) mentions a 25 x 45-cm aquamarine crystal fragment of gem quality. Guillemin and Mantienne (1988) report that the Andrade Museum in Maputo, Mozambique, contains a perfect 45-cm beryl crystal from Alto Ligonha.

In all, at least 20 major pegmatites and pegmatite groups have produced noteworthy beryl at Alto Ligonha, especially those clustered around the Entata granitic intrusion. The Naipa pegmatite, for example, has produced beryl associated with gem elbaite, muscovite, lepidolite and other lithium-containing minerals. The Colina pegmatite yielded 40 tons of ore-grade crystals of which 0.1% were aquamarine. The Murrapane and Itaia pegmatites were also important producers (Borges, 1957; Bandy, 1951).

Betafite [(Ca,Na,U)sub.2][(Ti,Nb,Ta).sub.2][O.sub.6](OH)

Betafite has been reported from the Ile pegmatite, in association with euxenite, allanite and monazite, and from the Ehiale-Namovela-Massive-Horta group in association with euxenite and samarskite (DSGM, 1974).

Bismuth Bi

Approximately 3 tons of native bismuth, bismuth sulfide and bismuth alteration products were removed from two pegmatites (Bandy, 1951). These minerals came from the inner intermediate lithia zone and from the associated alluvium and eluvium (Kun, 1965). Masses of euhedral, well-developed crystals from the Muiane mine show the forms {1011}, {0001}, {0112} and {0220} (Cotelo Neiva and Correia Neves, 1960).

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

A single pocket in the Naipa pegmatite yielded over 450 kg (half a ton) of bismuthinite and a little native bismuth (Bandy, 1951).

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

The Naipa pegmatite has yielded pockets containing 45 kg of greenish bismutite and brownish bismuth ochre (Bandy, 1951). Bismutite also occurs as an alteration product of bismuth and bismuthinite, and is widespread throughout the district. Fifteen different pegmatites and pegmatite groups have reported the presence of bismutite (DSGM, 1974). At the Muiane pegmatite it forms amorphous masses which are white to greenish to lemon-yellow in color (Cotelo Neiva and Correia Neves, 1960). Aires-Barros (1966) made a detailed study of some occurrences of bismutite in the Alto Ligonha and Alto Molocue pegmatites. Sahama and Lehtinen (1968) made a regional study, describing acicular habits, ghostlike remnants and pulverulent masses of honey-yellow to dark gray or greenish bismutite.

In 1958 one of us (MBD) saw nearly 2 tons of bismutite pseudomorphs from the Malolo pegmatite. The pseudomorphs showed a hexagonal prismatic habit lacking terminations, apparently after beryl or quartz crystals; many were hollow or with quartz occupying the core of the pseudomorphs. "Crystal" sizes ranged up to 5 cm in diameter and 10 cm long, with most around 2 x 5 cm.

Cassiterite Sn[O.sub.2]

Cassiterite was reported from the Piteia pegmatite by Bandy (1951), although he admitted not having personally seen the specimens. It has also been reported from the Muiane-Naipa group, the Ingela-Murrapane-Namicaia group, the Tulua-Marengo group, and the Naiume pegmatite (DSGM, 1974).

Churchite-(Y) [YPO.sub.4]*2[H.sub.2]O

Von Knorring (1977b) described specimens of churchite-(Y) from the Muiane pegmatite.

Clinobisvanite BiV[O.sub.2]

Von Knorring et al. (1973) described pucherite and a monoclinic dimorph from the Mutala pegmatite. The orange, well-formed, 2-mm crystals resemble pyramidal scheelite in habit. Multiple twinning occurs on (101), and (010), with perfect cleavage on {010}. The monoclinic dimorph was officially named clinobisvanite by Bridge and Pryce (1974), based on specimens from Yinnietharra, Western Australia. Had Von Knorring et al. proposed a name, it would have had precedence, and Mozambique would instead have been the type locality.

Clinochlore [(Mg,Al).sub.6]([Si.sub.3]Al)[O.sub.10][(OH).sub.8]

Goni and Guillemin (1964) observed iron-free clinochlore ("leuchtenbergite") as part of a suite of minerals (with microcline and muscovite) which have replaced tourmaline at Alto Ligonha. The clinochiore "locally forms a network in the microfissures of tourmaline crystals." The partially replaced tourmalines may also contain crystals of manganotantalite.

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

Cookeite probably occurs at the same pegmatites where other lithium minerals are abundant. One documented specimen, from Muiane, is a remarkable 8-mm single crystal in the Andrade Museum, Maputo, Mozambique (Guillemin and Mantienne, 1988). It is sometimes found coating and partially replacing crystals of red elbaite, lepidolite and muscovite (Cotelo Neiva and Correia Neves, 1960). Sahama et al. (1968) described specimens from the Muiane mine: large rosettes crystallized in an open vug, consisting of thin, six-sided, transparent, yellowish flakes to 1 cm across.

Corundum [Al.sub.2][O.sub.3]

Corundum was reported from the Niesse-Isabela mine area by DSGM (1974).

Elbaite Na[(Li,Al).sub.3][Al.sub.6][([BO.sub.3]).sub.3][Si.sub.6][O.sub.18][( OH).sub.4]

Magnificent red and green tourmaline crystals of the highest gem quality have been a hallmark of the district. Fine crystals in shades of blue, violet, brown, orange and yellow, even "tea-color" and "ecru," have also been found. Eight of the 27 principal mines and mine groups have produced significant tourmaline (DSGM, 1974), including the much-admired rubellite form Muiane, and beautiful green to blue-green crystals from Naipa. Many of the large red crystals have a green termination (Bandy, 1951).

Generally the green crystals are smaller, rarely over 4 cm, whereas the red to raspberry crystals can be quite large. A particularly large, terminated, rose-red crystal from Muiane measuring 42 cm is in the Andrade Museum, Maputo, Mozambique. A 10 x 30-cm red crystal is in the collection of the American Museum of Natural History in New York. A fine green crystal measuring 12 x 35 cm is held by the Smithsonian Institution (Guillemin and Mantienne, 1988), along with a remarkable 50-cm rubellite crystal from Muiane.

Crystal forms observed on Alto Ligonha tourmaline include {1120}, {1010}, {2130}, {5270}, {4150}, {7180}, {0110}, {0001}, {0221}, {0772}, {1011}, and {0112} (Cotelo Neiva and Correia Neves, 1960).

An electron microprobe analysis of a large rubellite crystal in the Jack Halpern collection was performed by Terry Wallace (University of Arizona); the mineral is confirmed as elbaite, with an Na:Ca ratio of 5:1.

Eosphorite [Mn.sup.2+]Al([PO.sub.4])[(OH).sub.2][H.sub.2]O

Correia Neves and Lopes Nunes (1968) described eosphorite, variscite, phosphosiderite, hureaulite, montebrasite, fluorapatite, amblygonite, triplite and bermanite from Alto Ligonha pegmatites.

Euclase BeAlSi[O.sub.4](OH)

Von Knorring et al. (1964) described euclase crystals from the Muiane pegmatite. Crystal forms observed include {010}, {210}, {120}, {111} and {121}.

Euxenite-(Y) (Y,Ca,Ce,U,Th)[(Nb,Ta,Ti).sub.2][O.sub.6]

Euxenite has been reported from six principal mines and mine groups (DSGM, 1974).

Fergusonite (Ce,Nd,La,Y)Nb[O.sub.4]

Fergusonite has been reported from the cluster of pegmatites that includes the Mugeba, Bere, Enluma, Maria, Macotaia and Namagoa bodies (DSGM, 1974).

Ferrocolumbite [Fe.sup.2]+[Nb.sub.2][O.sub.6]

Ferrocolumbite was a commercial product at a number of pegmatites. Ferrocolumbite and ferrotantalite, both black and visually indistinguishable, came out in the concentrates at the Muiane processing facility. The ferrocolumbite was then magnetically separated from the non-magnetic ferrotantalite. According to Kun (1965), crystals from the perthite zone tend to be large, whereas crystals from the albite-lithia zone are smaller, fan-like, tabular grains.

Ferrotantalite (Fe,Mn)[Ta.sub.2][O.sub.6]

Over 100 tons of what was then referred to loosely as "columbite-tantalite" or "columbotantalite" was produced from the district in the 1940's (Bandy, 1951). Most of this material generally had a Ta:Nb ratio of about 4:1, making it ferrotantalite by today's nomenclature. It was found in almost every complex pegmatite, and in commercial quantities in ten of the larger orebodies.

The crystals vary from rough to quite sharp, and from small grains to crystal masses weighing 1 kg or more. Fine crystals measuring 2.5 x 2.5 x 5 cm, from mines in the southern part of the district show a variety of interesting crystal forms. The best crystals came from the contact area between the mica and feldspar zones.

Cotelo Neiva and Correia Neves (1960) report crystals of "tantalite-columbite" having the following forms: tabular on {010} or instead on {100}, {130} on all crystals; to a lesser extent also {012}, {011}, {032}, {021}, {111}, {211}, {221}, {201}, {131} and {161}. Some crystals are twinned on (201) and others on (203); parallel aggregates are common.

Ferrotapiolite (Fe,Mn)[Ta.sub.2][O.sub.6]

Fine crystals of black ferrotapiolite to 8 kg have been reported from the Muiane pegmatite (Gaines et al., 1997). Ferrotapiolite is also known from the Malolo-Lice pegmatites (DSGM, 1974).

Florencite (Ce,La,Nd)[Al.sub.3][([PO.sub.4]).sub.2][(OH).sub.6]

A massive chunk of florencite from the Naipa pegmatite was collected by Mark Bandy and came later into the collection of the Los Angeles County Museum of Natural History. The mottled, cream-colored mass was identified by X-ray diffraction, therefore the exact species (florencite-(Ce), florencite-(Nd) or florencite-(La)) is not known.

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

Altered fluorapatite crystals occur at many pegmatites in the district, especially at Nahia where white crystals 30 cm across and 15 cm tall and blue-green 15 x 15-cm crystals were found (Bandy, 1951). Short prismatic crystals showing {1010}, {0001}, {1011} and {1120} were reported by Cotelo Neiva and Correia Neves (1960). Some fluorapatite is unusual in containing 0.21% Cd (Correia Neves and Lopes Nunes, 1968).

Fluorite [CaF.sub.2]

According to Bandy (1951), about 5 tons of fluorite concentrate were shipped from the Piteia pegmatite, where it occurred with other fluorine-containing minerals such as fluorapatite, topaz and lepidolite. It was found in deep green masses; 10-cm cleavage octahedrons were broken out by the miners. Cuboctahedral crystals were reported by Cotelo Neiva and Correia Neves (1960) from the Muiane mine.

Gadolinite [(Ce,La,Nd,Y).sub.2][Fe.sup.2+][Be.sub.2][Si.sub.2][O.sub.10]

Cotelo Neiva and Correia Neves (1960) report the occurrence of rare gadolinite at the Muiane mine. They do not specify whether it is gadolinite-(Ce) or gadolinite-(Y), but the presence of other Ce-Nd-La-containing minerals at Alto Ligonha makes gadolinite-(Ce) the more likely choice. It occurs as massive grains and prismatic crystals of a dark greenish brown color.

Garnet

Bandy (1951) reported that red to black non-gem garnets, massive and in crystals, had been found at several pegmatites in the district, especially at Naipa. Sinkankas (1981) also refers to garnet, as a component of the Muiane pegmatite. (See spessartine.)

Gibbsite Al[(OH).sub.3]

Correia Neves et al. (1969) identified gibbsite as a principal weathering product of microcline-perthite in the pegmatites of the Zambezia district.

Gold Au

Surprisingly, over 90 kg of native gold have been recovered from district pegmatites and the alluvial/eluvial deposits associated with them. A 75-gram specimen was reportedly taken from a quartz vein or pegmatite at Locuir (Bandy, 1951).

Most gold probably came from eluvial accumulations resulting from the breakdown of small quartz veinlets common throughout the schists, in close proximity to pegmatites. Weathered material from the two rock types can become mixed near the contact; for example, eluvial deposits of ferrocolumbite on the south slope of the Muiane pegmatite contain some gold from the schist. Gold is visible in the schist itself, and in the eluvium layer directly in contact with the schist, but never higher up in the depositional sequence.

Hafnon [HfSiO.sub.4]

In 1974, "zircon" crystals from tantalum-bearing pegmatites of the Morro Conco, Moneia and Muiane mines were shown to be the hafnium analog. Analyses yielded 69.78% [HfO.sub.2], sufficient to designate the material as a new species given the name hafnon. The crystals are zoned, with higher Hf content near the surface. Associations include cookeite and cleavelandite. The crystals, which have the same habit as zircon, are euhedral to irregular and occur in sizes up to 1 cm. They range in color from colorless to orange-red and brownish yellow. The mineral occurs in pegmatites enriched in Ta and Nb minerals, especially where the enrichment favors [Hf.sup.72]-[Ta.sup.73] over [Zr.sup.40]-[Nb.sup.41] (Correia Neves, et al., 1974).

Holmquistite ([Li.sub.2][Mg.sub.3][Al.sub.2])[Si.sub.8][O.sub.22][(OH).sub.2]

Barros (1972) reported the presence of holmquistite in the border zone of the Morrua pegmatite.

Hubnerite (Mn,[Fe.sup.3+],[Fe.sup.2+],Ti,Sn)(W,Nb,Ta)[O.sub.4]

Saari et al. (1968) described niobium and tantalum-rich hubnerite from the Nuaparra pegmatite. Crystals are opaque, dark gray to black, prismatic and poorly developed, with a semi-metallic luster, in sizes up to 3 cm.

Hureaulite [[Mn.sup.2+].sub.5][([PO.sub.4]).sub.2][[[PO.sub.3](OH)].sub.2]*4[H.s ub.2]O

Correia Neves and Lopes Nunes (1968) described hureaulite, montebrasite, fluorapatite, amblygonite, triplite, phosphosiderite, variscite, eosphorite and bermanite from Alto Ligonha pegmatites.

Hydroxylherderite CaBe([PO.sub.4])(OH,F)

Correia Neves and Lopes Nunes (1965) described herderite crystals from the Naipa pegmatite. Principal forms include {110}, {011}, {111}, {001}, {012}, {013}, {102}, {[104.sup.-]}, {123}? And {[116.sup.-]}. Lacking analyses, it must be assumed to be hydroxylherderite.

Ilmenorutile [(Ti,Nb,[Fe.sup.3+]).sub.3][O.sub.6]

Ilmenorutile and its tantalum analog, struverite, were described from the Nampoca pegmatite by Lima de Faria and Quadrado (1966). Crystals sometimes show a microscopic intergrowth with columbite.

Ixiolite [([Fe.sup.2+],[Fe.sup.3+],Ta,Nb,Sc,Ti,Sn,Zr,Mn).sub.4][O.sub.8]

Borisenko et al. (1969) analyzed a scandium-bearing tantaloniobate from Mozambique and found it to be scandium-titanium-zirconium-bearing ixiolite. It occurs in rounded grains to over 1 cm, having a dull gray-black color. Von Knorring et al. (1969) described what is apparently the same material, specifying the locality as the Naquissupa pegmatite. The locality is currently known as Nanro, and continues to yield black hemispheres of ixiolite.

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

A large percentage of the pegmatites in the district are deeply kaolinized. Especially large quantities have been found in the Boa Esperanca, Murropoci, Nuaparra, Namirrapo, Mucholone and Marropino pegmatites (DSGM, 1974).

Lepidolite Li-Mica

After muscovite, lepidolite was the most important ore mineral in the district. It was found in masses of high purity at several pegmatites; the Naipa pegmatite, for example, contained a bed of almost pure lepidolite measuring 3 meters thick, and 11 meters across.

Bandy (1951) reports lepidolite with a fine lavender color, in interlocking books, radiating columns and large, tapering crystals. At the Naipa mine these individual crystals reach 18 cm in length and 5 x 10 cm across. Cleavages 36 cm across were found at the Muiane mine, and 30 cm across at the Piteia mine. Cotelo Neiva and Correia Neves (1960) report large cleaved slabs to 60 cm across from the Muiane mine. Crystals show {001}, {110} and {010}. It is sometimes found in cylindrical masses of crystals 13 to 40 cm across and 20 to 80 cm long, rounded over the top, as if having once encrusted a large, now-gone crystal. At the Naipa mine it was found as spherical, radial aggregates to over 14 cm.

Magnetite [Fe.sup.2+][[Fe.sup.3+].sub.2][O.sub.4]

Coarsely crystalline magnetite is the only accessory mineral in the barren, simple pegmatites of the granitic terranes (Hutchinson and Claus, 1956).

Manganotantalite (Mn,Fe)[(Ta,Nb).sub.2][O.sub.6]

Fine and sometimes large, tabular to blocky crystals of manganotantalite have been reported from the Morrua, Muiane and Marropino pegmatites; some specimens show sharp, transparent twins (Gaines et al., 1997). The V-shaped twins, of which we have seen several, are dark red and measure about 1.5 cm. They have a broad (100) face in common, are striated parallel to (001), and are twinned on (021). On the specimen we measured the bordering faces include (010) and (001), with different modifications on the left-hand member of the twin ((101), (201), (120)) vs. the righthand member ((102), (301), (140)). An excellent Morrua-mine crystal measuring 7 cm is in the collection of the Natural History Museum, London (Guillemin and Mantienne, 1988). Von Knorring et al. (1966) analyzed crystals from the Morrua mine and found them to be the closest yet known to having an ideal formula (Ta:Nb = 99:1, Mn:Fe = 97:3). A 9.8 x 10-cm "floater" crystal from the Cunco pegmatite, and an 11 x 14 x 14.5-cm euhedron (7 kg) from the Naip a pegmatite are in the Desmond Sacco collection.

Microcline [KAlSi.sub.3][O.sub.8]

Amazonite, the bluish green variety of microcline, has been reported from the Monapo, Carapira, Leonora, Mueterere, Namacala, Lice and Malolo pegmatites (DSGM, 1974). Cotelo Neiva and Correia Neves (1960) described a 1-meter crystal showing (001), (010), (110), (110), (101) and (130).

Microlite [(Ca,Na).sub.2][Ta.sub.2][O.sub.6](O,OH,F)

Microlite has been reported from six major pegmatites and pegmatite groups including the Marropino, Morrua, Nampoca, Napir and Munhamola pegmatites (DSGM, 1974). At the Munhamola pegmatite near Alto Molocue, microlite occurs as sharp, lustrous crystals to 2.5 cm, associated with tabular lepidolite crystals exceeding 1 cm across the cleavage face. The microlite crystals are nearly black in overall appearance, but are actually a very dark, translucent yellow as revealed by internal fractures. The habit is a combination mainly of the dodecahedron and cube, modified by small octahedron faces and very small faces of two trapezohedron forms.

Molybdenite Mo[S.sub.2]

Molybdenite has been reported from the Maria III pegmatite (DSGM, 1974).

Monazite (Ce,La,Nd,Th)[PO.sub.4]

Over 680 kg of monazite have been produced in the Alto Ligonha district, especially at Muiane, with allanite and samarskite (Bandy, 1951). It is a common mineral, noted from a dozen different pegmatites and pegmatite groups (DSGM, 1974). Cotelo Neiva and Correja Neves (1960) found crystals only very rarely, in a tabular habit on (100), with (100), (101), [111), (001), and (212). Bancroft (1984) described crystals up to 10 cm in size (1), but said the mineral usually occurs in irregularly shaped masses and as tiny crystals with allanite.

Montebrasite LiAl([PO.sub.4])(OH,F)

Correia Neves and Lopes Nunes (1968) described montebrasite, fluorapatite, amblygonite, triplite, hureaulite, phosphosiderite, variscite, eosphorite and bermanite from Alto Ligonha pegmatites.

Montmorillonite [(Na,Ca).sub.0.3][(Al,Mg).sub.2][Si.sub.4][O.sub.10][(OH).sub.2]*n[H. sub.2]O

Montmorillonite clay was reported as rare flesh-colored masses at the Muiane mine (Cotelo Neiva and Correia Neves, 1960).

Muscovite [KAl.sub.2][AlSi.sub.3][O.sub.10][(OH).sub.2]

Muscovite was for many years the principal ore mineral in the district, over a thousand tons having been produced as of 1951 (Bandy, 1951). Most of the early production came from the Murrapane and Boa Esperanza mines. Books measuring over 30 cm across were not uncommon.

Various colors of mica were recovered, including a gemmy red variety known as "ruby mica." Black and brown micas assumed to be biotite and phlogopite were found as well (but definitive analyses are lacking).

Tabular and occasionally prismatic crystals have been described by Cotelo Neiva and Correia Neves (1960) from Muiane. Forms observed include (001), (110), (010), (101), [023) and (043). "Curious spherical concentrations" are sometimes found surrounding a crystal of green elbaite, schorl or beryl. Neiva (1978) described a barian, chromium-bearing variety from Alto Ligonha.

Oligoclase (Na,Ca)[(Si,Al).sub.4][O.sub.8]

Cotelo Neiva and Correia Neves (1960) reported cleavable masses and pale gray crystals of oligoclase from Muiane; crystal formsinclude (001), (110), (110), (010), and (130). It was found also as inclusions in microcline, and also with its own rare inclusions of euhedral zircon.

Orthoclase [KalSi.sub.3][O.sub.8]

Orthoclase occurs in cleavable masses up to 76 cm across in some of the simple pegmatites. Fine, sharp crystals of pink to cream color measuring up to 10 cm were found at Piteia (Bandy, 1951). Carlsbad twins are common. Crystal forms observed include (001), (010), (110), (130), (101), (201) and (111) (Cotelo Neiva and Correia Neves, 1960). Thousands of tons of massive orthoclase, microcline and albite were stockpiled as of 1949.

Petalite [LiAlSi.sub.4][O.sub.10]

Petalite is reported as one of several lithium-bearing minerals (including also lepidolite, amblygonite and spodumene) known to occur at seven pegmatites and pegmatite groups (DSGM, 1974).

Phosphosiderite [Fe.sup.3+][PO.sub.4]*2[H.sub.2]O

Correia Neves and Lopes Nunes (1968) described phosphosiderite, hureaulite, montebrasite, fluorapatite, amblygonite, triplite, variscite, eosphorite and bermanite from Alto Ligonha pegmatites.

Plumbomicrolite [(Pb,Ca,U).sub.2][Ta.sub.2][O.sub.6](OH)

Plumomicrolite has been reported from the Naipa pegmatite by Leal Gomes (1999a); it contains 25.03 wt. % PbO.

Pollucite (Cs,NA)[[AlSi.sub.2][O.sub.6]]*n[H.sub.2]O

Pollucite has been reported from the Morrua, Mocachaia, Alata, Intotcha and Nahora pegmatites (DSGM, 1974). Khalili and Von Knorring (1977) described specific examples.

Pucherite [BiVO.sub.4]

Von Knorring et al. (1973) described two types of [BiVO.sub.4] occurring as orange, well-formed crystals to 2 mm in bismutite from the Mutala pegmatite. The orthorhombic phase was identified as pucherite; the monoclinic phase was a new species but remained unnamed until Bridge and Pryce (1974) described the same material from Western Australia, naming it clinobisvanite.

Pyrochiore [(Na,Ca).sub.2][Nb.sub.2][O.sub.6](OH,F)

Pyrochiore crystals, octahedral and yellowish brown in color, were reported from the Mocachaia pegmatite (Cotelo Neiva and Correia Neves, 1960). It appears to be partially pseudomorphically replaced by an unknown black mineral.

Quartz [SiO.sub.2]

Although notable quartz crystals are rare in most pegmatites in the district, magnificent crystals to more than a meter were found at Nahia, and fine crystals 15 cm in diameter were discovered at Cavala. In some vugs, fine crystals of quartz and orthoclase or albite were found. Rose quartz (massive) came from Macula.

The well-zoned Muiane pegmatite contained large masses of lepidolite and large quartz crystals, some of fine specimen quality, up 1.8 meters and 900 kg (Sinkankas, 1981). The color ranges from black to pale brown, colorless, milky and rose. Parallel crystal aggregates are common. Large scepters of smoky quartz on colorless quartz are also known. Forms generally include (1011), (1010), (0111), plus occasionally {10.0.10.1}, {0.11.11.1}, (4041), (5051), (0551), (2111), (1121), (5141), (1347) and (1012), Brazil-law twins are common (Cotelo Neiva and Correia Neves, 1960). Included species noted: zircon, rutile, muscovite and tourmaline. Fluid inclusions were also fairly common in Muiane quartz.

Rutile [TiO.sub.2]

Superb, sharp, lustrous crystals of rutile to over 5 cm in diameter have been reported from the Ribaue area (Bandy, 1951). Examples have also been recorded from the Macula, Nahaji, Morrua, Melela and Namarripa pegmatite (DSGM, 1974).

Samarskite-(Y) [(Y,Ce,U,[Fe.sup.3+]).sub.3][(Nb,Ta,Ti).sub.5][O.sub.16]

Eight tons of samarskite, a remarkable quantity, were produced from three pegmatites (Bandy, 1951). Excellent, sharp crystals to about 2 cm were found at Macotaia (where it constituted the only commercially valuable mineral), and some larger ones came from Muiane. Other occurrences include the Boa Esperanca, Ehiale, Namovela, Massive, Horta, Mtomoti, Namivo, Tomeia, Nampoca and Mugeba pegmatites (DSGM, 1974). At the Ingela and Mirrucue pegmatites it was found as euhedral crystals showing well-developed {100}, {010} and {101} with minor {120} and {111}. Some crystal clusters are fan-shaped. The mineral appears to be metamict (Cotelo Neiva and Correia Neves, 1960). Bancroft (1984) reported sharp crystals of samarskite to 4 cm from the Macotaia pegmatite. Alto Ligonha samarskite has been isotopically age-dated at 408 to 465 million years (Kun, 1965).

Scapolite 3NaAl[Si.sub.3][O.sub.8]*NaCl

Scapolite (not specified as marialite or meionite) was reported from the Niessa-Isabela pegmatites (DSGM, 1974). There is a fine, gemmy, terminated crystal of pale tan color, measuring 2.8 cm, in the William Larson collection.

Schorl Na[[Fe.sup.2+].sub.3][Al.sub.6][([BO.sub.3]).sub.3][Si.sub.6][O.sub.1 8][(OH).sub.4]

Small, black tourmaline crystals, presumably schorl, have been found embedded in mica and feldspar along the border zone of simple and mica-rich pegmatites (Bandy, 1951). Attractive, deep black crystals penetrating quartz crystals occur at the Muiane mine.

Spessartine [[Mn.sup.2+].sub.3][Al.sub.2](Si[O.sub.4])

Cotelo Neiva and Correia Neves (1960) report euhedral crystals of red-brown spessartine from the Muiane mine. Forms include [110] and [211].

Spodumene LiAl[Si.sub.2][O.sub.6]

Spodumene, including the varieties hiddenite and kunzite, as well as other lithium minerals such as lepidolite, petalite and amblygonite, have been reported from seven major pegmatites and pegmatite groups (DSGM, 1974), including the Mujane pegmatite (Sinkankas, 1981). It occurs in large, prismatic crystals dominated by {100}. Quadrado and Amoros (1965) described spodumene from the Namacotche pegmatite as being colorless and transparent with a prismatic habit and showing etch figures on the {110} faces. Associated species include beryl, albite, lepidolite and bismuth minerals.

Stibiomicrolite [(Sb,Ca,Na).sub.2][(Ta,Nb).sub.2][O.sub.7]

The Naipa pegmatite appears to be the first known occurrence of well-crystallized (that is, at least subhedral, macroscopic) stibiomicrolite. The two known specimens are rather tabular due to restricted growth in the interstices between albite plates.

One specimen, 3.5 cm across and about 8 mm thick, appears to be flattened perpendicular to the 2-fold axis (i.e., on the dodecahedron). On one end it shows lustrous and sharp octahedron faces with narrow dodecahedron modifications. Most of the crystal is blackish in color but gemmy areas seen through the good crystal faces are demantoid-green. The second crystal, 2.9 cm across, is also/contacted over much of its surface but appears to show octahedron and dodecahedron faces on one end. The color is a similar dark green, but the crystal is flattened roughly perpendicular to the 4-fold axis.

The two crystals were collected by Jose Rodriguez Rosa and identified by electron microprobe at the Universidade do Minho in Braga, Portugal.

Stibiotantalite (Sb,Bi)(Ta,Nb)[O.sub.4]

Bandy (1951) reported that most stibiotantalite crystals from Alto Ligonha are rather small, 1 cm or less, but the largest known crystal (a sharp but damaged, blocky crystal in the Smithsonian) is 10 x 10 cm. A 10 x 10.5-cm crystal, partially gemmy, from the Morrua pegmatite is in the Desmond Sacco collection. This crystal and many other smaller examples came from the Muiane pegmatite. Another Muiane crystal, this one weighing 2 kg, is in the collection of the Andrade Museum, Maputo, Mozambique (Guillemin and Mantienne, 1988).

Some of the small crystals are gemmy and colorless to pale brown; larger crystals are blackish to opaque with translucent to transparent zones. At Muiane it occurs with red elbaite, pink beryl and manganotantalite (Gaines et al., 1997).

Crystal forms noted on stibiotantalite from the Muiane mine include (010), {110}, {101}, plus occasionally {111}, {130}, {170}, {150}, {012} and {332}. Some are twinned on {010} (Cotelo Neiva and Coreia Neves, 1960).

Stibiotantalite crystals from the Maridge pegmatite are a grayish yellow in color and quite translucent. They occur in sharp, blocky crystals dominated by {010}, {100} and {302}, and measuring 1 to 5.2 cm. The {010} faces are striated parallel to c, and the {302} and {201} faces are commonly preferentially coated by a thin, epitaxial layer of a black, opaque mineral, presumably manganotantalite or ferrotantalite. The only other association visible is lepidolite.

Struverite [(Ti,Ta,[Fe.sup.3+]).sub.3][O.sub.6]

Struverite and its niobian analog, ilmenorutile, were described from the Nampoca pegmatite by Lima de Farina and Quadrado (1966).

Thorianite Th[O.sub.2]

Thorianite has been identified from the Namivo-Tomeia-Nampoca group of pegmatites (DSGM, 1974).

Thorogummite (?) (Th,REE,U)(Si,Al)[O.sub.4][(OH).sub.4]

Cotelo Neiva and Correia Neves (1960) reported a new mineral from Muiane which they named mozambikite. The description stated that the mineral is yellow-brown, occurring in octahedral crystals with a specific gravity of 5.24. A preliminary chemical analysis yielded Th[O.sub.2] = 58.80%, [V.sub.3][O.sub.8] = 6.04%, [R.sub.2][O.sub.3] rare earth oxides = 8.60%, [Al.sub.2][O.sub.3] = 4.40%, Si[O.sub.2] = 11.00%, and [H.sub.2]O = 5.33%, plus less than a percent of CaO and [Fe.sub.2][O.sub.3]. A more complete study was promised but never published; the description as it stood was unanimously rejected by the International Mineralogical Association. It is probably a variety of thorogummite.

Topaz [Al.sub.2]Si[O.sub.4])[(F,OH).sub.2]

Topaz crystals to more than a meter long and 25 cm wide have been found at Piteia; they are opaque white to yellowish white and rough. Smaller colorless, translucent crystals were found at the same mine (Bandy, 1951). The mineral is also recorded from the Ingela-Murrapane-Namicaia group of pegmatites (DSGM, 1974), and occurred in fine crystals at the Muiane pegmatite (Sinkankas, 1981). Muiane crystals tend to be colorless to gray and prismatic, with dominant {110} and {001}, and minor {120} and {021} (Cotelo Neiva and Correia Neves, 1960).

Topaz crystals were also found at the Gelo pegmatite in the 1970's, some weighing 2 to 4 kg; they were colorless and partially gemmy.

In 1967, while visiting the Muinne mine treatment plant, one of us (MBD) saw sky-blue topaz crystals from Mirrucue being bagged for shipment as industrial beryl. When the superintendent was informed that the blue material was actually topaz worth many times the value of beryl, he vigorously disputed the identification. "We've shipped more than 5 tons of this kind of beryl to the U.S.," he said, "and the buyers have never complained!"

Triplite [([Mn.sup.2+],[Fe.sup.2+],Mg,Ca).sub.2]([PO.sub.4])(F,OH)

Triplite and other manganese minerals are reported to occur at two pegmatites and perhaps others (Bandy, 1951). Correia Neves and Lopes Nunes (1968) later reported triplite and other phosphates from Alto Ligonha pegmatites.

Uraninite U[O.sub.2]

Uraninite, in association with ferrotantalite, fergusonite, euxenite, samarskite and monazite, is known from the cluster of pegmatite bodies that includes the Mugeba, Bere, Enluma, Maria, Muacotaia and Namagoa pegmatites (DSGM, 1974).

Uranmicrolite [(U,Ca,Ce).sub.2][(Ta,Nb).sub.2][O.sub.6](OH,F)

Uranmicrolite has been reported from the Naipa pegmatite by Leal Gomes (1999a); it contains 10.47 wt.% U[O.sub.2].

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

Correia Neves and Lopes Nunes (1968) described variscite, phosphosiderite, hureaulite, montebrasite, fluorapatite, amblygonite, triplite, eosphorite and bermanite from Alto Ligonha pegmatites.

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

Xenotime-(Y) has been reported from a number of pegmatites and groups including the Boa Esperanca, the Guilherme-ComuaMuetia group, the Murropoci-Nuaparra group, and the Namivo-Tomeia-Nampoca group (DSGM, 1974). Sahama et al. (1973) analyzed xenotime from the Morrua pegmatite and found that it occurs in two distinct generations, has an unusually high ratio of yttrium to lanthanides (78:22), and is strongly enriched in gadolinium.

Yttrocolumbite-(Y) (Y,U,[Fe.sup.2+])(Nb,Ta)[O.sub.4]

Yttrocolumbite was described by Lepierre (1937) as a new mineral from an unspecified pegmatite in Mozambique. Considering the abundance of other rare earth minerals in the Alto Ligonha district, it is likely that the type locality is in this area. The mineral is black with a brilliant luster, and is said to resemble ampanagabite.

Zircon ZrSi[O.sub.4]

Zircon has been reported from the Niesse-Isabela pegmatites, in association with beryl, scapolite, allanite and corundum (DSGM, 1974). Cotelo Neiva and Correia Neves (1960) report reddish brown, well-formed zircon from the Muiane mine, showing the form {111} (dominant) with {100}, {001} and {311} (minor).

Unknowns

Cotelo Neiva and Correia Neves (1960) reported several unknown or unidentified species, including:

(1) "Mineral A," in well-developed, black, orthorhombic crystals with resinous luster. It was presumed to be a tantalate of some kind (strongest x-ray lines: 2.495 (10), 1.470 (10), 2.060 (4), 1.675 (3) and 1.600 (3)).

(2) "Mineral B," in black, apparently orthorhombic crystals dominated by {001}, {100} and {110}. It looks like columbite-tantalite but has differing principal X-ray powder diffraction lines (2.72 (10), 4.20 (6), 1.70 (5), 1.458 (5)).

(3) Alteration product of stibiotantalite, yellow and powdery (strongest X-ray lines: 2.95 (10), 1.625 (8), 2.75 (4), 2.14 and 1.94 (4)).

(4) A black, octahedral, cubic-isotropic, radioactive mineral with [a.sub.0] = 8.18A; it occurs surrounding a core of pyrochlore from the Mocachaia pegmatite.

CURRENT STATUS

There is currently much activity going on in the Alto Ligonha pegmatites. The government has issued a number of concessions to people willing to work various pegmatites, and is encouraging development in the district.

Alexander Dikov, a Bulgarian geologist (P.O. Box 66, 1404 Sophia; e-mail: dikov@mail.techno-link.com), has the Nuapara II concession, consisting of five small pegmatites collectively referred to as Nuaparra. Attractive, large quartz crystals with green elbaite are among its products.

Operating under the company name of Intergeoresource Ltd., Dikov distributes specimens from his own concession and also from other Alto Ligonha pegmatites currently in operation. These include the main pegmatite at Muiane (red elbaite in coarse-textured lepidolite, pale yellow cookeite, and yellow microlite crystals to 6 mm), Nacuissupa (citrine quartz crystals, green elbaite in a sheaf-like habit to over 10 cm, and dark smoky quartz crystals), Manica (blackish, thick tabular stibiotantalite crystals to 3 cm), Nanro (the sole locality for the black hemispheres of ixiolite to 1 cm, as well as green elbaite and large colorless/citrine zoned quartz crystals), Mutala (quartz crystals on albite, pale pink beryl crystals in thick tabular habit to more than 10 cm), Namacotcha (pale green elbaite crystals with pink tips, blackish green elbaite with steep rhombohedral tenninations and indicolite-blue interiors, to 10 cm), Conco (black beryl, schorl crystals and acicular schorl inclusions in quartz crystals) and Nahor a (green to black elbaite crystals on quartz, spodumene in magenta, green and colorless crystals, "watermelon" tourmaline crystals).

Two Portuguese nationals, Jose and Sebastian Rodriguez Rosa (brothers), have the concession on the Naipa and Namacoche pegmatites. They operate under the company name Geofil Ltda. (Alto da Bela Vista 2-A, 2750 Cascais, Portugal).

The Naipa has lately been particularly prolific, yielding large and spectacular clusters of blue-green tourmaline crystals, as well as interesting crystals of yellow microlite octahedrons to 2 cm, blackish yellow microlite cuboctahedrons to 3 cm, black stiblocolumbite and manganocolumbite crystals to 4 cm, and flattened, dark green stibiomicrolite crystals to 3.5 cm. During 1998 and 1999 the Naipa mine was the leading producer of pegmatite minerals (mostly niobium-tantalum concentrates, gem beryl, gem elbaite, microlite, manganocolumbite and herderite) in Mozambique (A. A. Leal Games, pers. comm.). The deposit is the focus of new studies on pegmatite structure and paragenesis, and on Nb-Ta minerals, being undertaken by the Earth Science Department of Minho University, Portugal (see Leal Gomes, 1999a, 1999b).

From Namacotcha some attractive pink beryl crystals have recently appeared. They measure up to 10 cm across and are rather flattened perpendicular to the c axis (in the typical pink beryl habit).

Tabular crystals of reddish black manganotantalite to 10 cm have also been coming lately from Morrua and Muiane. Active mining continues at many sites, and more specimens should be forthcoming.

CONCLUSIONS

The Alto Ligonha pegmatite field is clearly among the most mineralogically interesting pegmatite areas in the world, and has yielded a substantial quantity of collector-quality crystal specimens. Many small pegmatite bodies surely remain unworked or undiscovered, and others continue to be mined on a small scale. Specimen production is likely to continue on a limited and sporadic basis indefinitely.

ACKNOWLEDGMENTS

The authors wish to thank R. Peter Richards for generating the crystal drawings. Abraham Rosenzweig and Bruce Cairncross reviewed the manuscript and offered helpful suggestions. Information and specimens for study and photography were graciously provided by Keith Proctor, Tom Moore, Alexander Dikov, Carl Francis (Harvard Mineralogical Museum), Jose Rodriguez Rosa, John S. White (from the collection of the late Richard V. Gaines), Jack Halpern, Gene Meiran, and Shirley Wetmore (University of Arizona Mineral Museum). The tourmaline analysis was kindly provided by Terry Wallace (University of Arizona). We are especially grateful to those who supplied specimen photography: George Harlow and Joseph J. Peters (American Museum of Natural History), F. John Barlow, Jeff Post (Smithsonian Institution), Anthony Kampf (Natural History Museum of Los Angeles County), Bruce Cairncross (of specimens in the Desmond Sacco collection), Jeff Scovil, Nelly Bariand, and Traudel Sachs (from the photo files of the late Karl Hartman n).

(1.) Ed. Note: Author MBD was a part of those investigations, described in his memoir, An African Name, published in 1999 by Peanut Butter Publishing of Seattle, Washington. (ISBN # 0-89716-867-4)

(2.) The arrow ([rightarrow]) indicates "followed by"; the plus (+) indicates "simultaneous with."

(3.) Extracted from the author's forthcoming books: An African Name and An African Career.

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Table 1. The most important pegmatite mines in the Alto Ligonha area, and the most notable minerals found at each pegmatite

(see map for locations of the numbered groups). Data compiled from DSGM (1974)

Carta de Jazigos e Ocorrencias Minerals, and other sources.

Group 1: Mines: Muiane, Naipa, Maridge, Nanro, Nacuissupa, Nihire.

Minerals: Tourmalines, beryl gems (1), beryl, manganotantalite, stibiotantalite, lithium minerals (2), mica, bismutite, bismuth, bismuthinite, monazite, stibiomicrolite, cassiterite, quartz gems (3), garnet, topaz, zircon, cookeite, samarskite.

Group 2: Mines: Ingela, Murrapane, Namicaia.

Minerals: Beryl gems, beryl, mica, ferrotantalite-ferrocolumbite, cassiterite, bismutite, topaz, quartz gems.

Group 3: Mines: Piteia Nahia, Mirrucue.

Minerals: Ferrotantalite-ferrocolumbite, quartz, quartz gems, topaz, lithium minerals, bismutite, mica, monazite, cassiterite, fluorite, fluorapatite, orthoclase.

Group 4: Mines: Monapo, Carapira.

Minerals: Amazonite, beryl gems.

Group 5: Mines: Tulua, Marengo.

Minerals:Tourmalines, cassiterite.

Group 6: Mines: Leonora, Mueterere, Namacala

Minerals: Tourmalines, beryl, amazonite, allanite.

Group 7: Mines: Niesse, Isabela.

Minerals: Beryl, mica, zircon, scapolite, allanite, corundum.

Group 8: Mines: Boa Esperanca.

Minerals: Kaolin, beryl, ferrotantalite-ferrocolumbite, zenotime, samarskite, monazite, euxenite.

Group 9: Mines: Guiherme, Comua, Muetia, Giline, Culahipa.

Minerals: Euxenite, monazite, xenotime, allanite.

Group 10: Mines: Ehiale, Namovela, Massive, Horta.

Minerals: Betafite, euxenite, samarskite.

Group 11: Mines: Macotaia, Mtomotiti.

Minerals: Ferrotantalite-ferrocolumbite, monazite, bismutite, samarskite.

Group 12: Mines: Muhano, Majamala, Cochiline.

Minerals: Beryl, ferrotantalite-ferrocolumbite, bismutite, tourmalines, monazite, zircon.

Group 13: Mines: Murropoci, Nuaparra, Namirrapo, Mucholone.

Minerals: Beryl, beryl gems, tourmalines, mica, bismutite, ferrotantalite-ferrocolumbite, microlite, lithium minerals, kaolin, xenotime.

Group 14: Mines: Macula, Nahaji.

Minerals: Beryl, ferrotantalite-ferrocolumnite, rutile.

Group 15: Mines: Mocachaia, Alata, Intotcha, Nahora.

Minerals: Beryl, ferrotantalite-ferrocolumbite, bismutite, beryl gems, tourmalines, monazite, mica, lithium minerals, zircon, pollucite.

Group 16: Mines: Namacotcha, Conco, Napire, Nassupe, Munhamola, Moneia.

Minerals: Beryl gems, beryl, lithium minerals, microlite, zircon, tourmalines.

Group 17: Mines: Lice, Malolo.

Minerals: Beryl, ferrotantalite-ferrocolumbite, bismutite, amazonite, black beryl, beryl gems, ferrotapiolite.

Group 18: Mines: Maria, Uelele, Namarrela, Mecassa.

Group 19: Mines: Maria III.

Minerals: Beryl, beryl gems, tourmalines, ferrotantalite-ferrocolumbite, microlite, bismutite, monazite.

Minerals: Emeralds, molybdenite.

Group 20: Mines: Namivo, Tomeja, Nampoca.

Minerals: Beryl, ferrotantalite-ferrocolumbite, thorianite, bismutite, monazite, microlite, zircon, samarskite, euxenite, beryl gems, black beryl, xenotime.

Group 21: Mines: Niane.

Minerals: Emeralds.

Group 22: Mines: lie.

Minerals: Betafite, euxenite, allanite, monazite, bismuthinite.

Group 23: Mines: Morrua.

Minerals: Microlite, manganotantalite, beryl gems, beryl, bismutite, lithium minerals, pollucite, monazite, rutile.

Group 24: Mines: Naiume.

Minerals: Beryl, ferrotantalite-ferrocolumbite, cassiterite, bismutite.

Group 25: Mines: Melela, Namarripa.

Minerals: Beryl, emeralds, ferrotantalite, bismutite, monazite, rutile.

Group 26: Mines: Marropino.

Minerals: Microlite, lithium minerals, bismutite, kaolin, manganotantalite, beryl and beryl gems, zircon.

Group 27: Mines: Mugeba, Bere, Enluma, Maria, Muacotaia, Namagoa.

Minerals: Ferrotantalite, euxenite, samarskite, monazite, fergusonite, uraninite, beryl.

(1.) Beryl gems include gem-grade blue-green (aquamarine), pink (morganite), golden yellow (heliodor) beryl and green beryl.

(2.) Lithium minerals include lepidolite, petalite, amblygonite, spodumene (green and lilac).

(3.) Quartz gems include colorless, smoky, rose and citrine quartz of gem quality.
Table 2. Production from the Alto Ligonha
pegmatite field, 1937-1962 (Kun, 1965).
                     Production   Production
                     1937-1958       1962
Beryl                 7,300 tons     440 tons
Columbite-Tantalite     570          110
Tourmaline              1.4            ?
Lithium ore          10,300          200
Other micas             150            1
Samarskite               20            ?
Bismutite                20           15
Monazite                 15            ?
Kaolin                  650            ?
Table 3. Pegmatite minerals of
the Alto Ligonha district.
Elements
  Bismuth              Bi
  Gold                 Au
Sulfides
  Bismuthinite         [Bi.sub.2][S.sub.3]
  Molybdenite          Mo[S.sub.2]
Fluorides
  Fluorite             Ca[F.sub.2]
Oxides, Hydroxides
  Cassiterite          Sn[O.sub.2]
  Corundum             [Al.sub.2][O.sub.3]
  Gibbsite             Al[(OH).sub.3]
  Hematite             [Fe.sub.2][O.sub.3]
  Magnetite            [Fe.sup.2+][[Fe.sup.3+].sub.2]
                       [O.sub.4]
  Rutile               Ti[O.sub.2]
  Thorianite           Th[O.sub.2]
  Thorogummite (?)     (Th,REE,U)(Si,Al)[O.sub.4]
                       [(OH).sub.4]
  Uraninite            U[O.sub.2]
Carbonates
  Bismutite            [Bi.sub.2](C[O.sub.3])
                       [O.sub.2]
Silicates
  Albite               NaAl[Si.sub.3][O.sub.8]
  Allanite-(Ce)        [(Ce,Ca,Y).sub.2]
                       [(Al,[Fe.sup.2+],[Fe.sup.3+]).sub.3]
                       [(Si[O.sub.4]).sub.3](OH)
  Andalusite           [Al.sub.2]Si[O.sub.5]
  Beryl                [Be.sub.3][Al.sub.2]
                       [Si.sub.6][O.sub.18]
  Clinochlore          [(Mg,Al).sub.6]([Si.sub.3]Al)
                       [O.sub.10][(OH).sub.8]
  Cookeite             Li[Al.sub.4]([Si.sub.3]Al)
                       [O.sub.10][(OH).sub.8]
  Elbaite              Na[(Li,Al).sub.3][Al.sub.6]
                       [([BO.sub.3]).sub.3]
                       [Si.sub.6][O.sub.18][(OH).sub.4]
  Euclase              BeAlSi[O.sub.4](OH)
  Gadolinite-(Ce)      [(Ce,La,Nd,Y).sub.2]
                       [Fe.sup.2+][Be.sub.2]
                       [Si.sub.2][O.sub.10]
  Hafnon               HfSi[O.sub.4]
  Holmquisite          ([Li.sub.2][Mg.sub.3][Al.sub.2])
                       [Si.sub.8][O.sub.22][(OH).sub.2]
  Kaolinite            [Al.sub.2][Si.sub.2][O.sub.5]
                       [(OH).sub.4]
  Lepidolite           Li-mica
  Microcline           KAl[Si.sub.3][O.sub.8]
  Montmorillonite      [(Na,Ca).sub.0,3]
                       [(Al,Mg).sub.2][Si.sub.4][O.sub.10]
                       [(OH).sub.2] . n[H.sub.2]O
  Muscovite            K[Al.sub.2]Al[Si.sub.3][O.sub.10]
                       [(OH).sub.2]
  Oligoclase           (Na,Ca)[(Si,Al).sub.4][O.sub.8]
  Orthoclase           KAl[Si.sub.3][O.sub.8]
  Petalite             LiAl[Si.sub.4][O.sub.10]
  Pollucite            (Cs,Na)[Al[Si.sub.2][O.sub.6]] .
                       n[H.sub.2]O
  Quartz               Si[O.sub.2]
  Scapolite series     3NaAl[Si.sub.3][O.sub.8] . Nacl
  Schorl               Na[[Fe.sup.2+].sub.3]
                       [Al.sub.6][([BO.sub.3]).sub.3]
                       [Si.sub.6][O.sub.18][(OH).sub.4]
  Spessartine          [[Mn.sup.2+].sub.3] [Al.sub.2]
                       [(Si[O.sub.4]).sub.3]
  Spodumene            LiAl[Si.sub.2][O.sub.6]
  Topaz                [Al.sub.2]Si[O.sub.4]
                       [(F,OH).sub.2]
  Zircon               ZrSi[O.sub.4]
Niobates, Tantalates
  Betafite             [(Ca,Na,U).sub.2][(Ti,Nb,Ta).sub.2]
                       [O.sub.6](OH)
  Euxenite-(Y)         (Y,Ca,Ce,U,Th)[(Nb,Ta,Ti).sub.2]
                       [O.sub.6]
  Fergusonite          (Ce,Nd,La,Y)Nb[O.sub.4]
  Ferrocolumbite       (Fe,Mn)[Nb.sub.2][O.sub.6]
  Ferrotantalite       (Fe,Mn)[Ta.sub.2][O.sub.6]
  Ferrotapiolite       Fe[(Ta,Nb).sub.2][O.sub.6]
  Hubnerite            (Mn,[Fe.sup.3+],[Fe.sup.2+],
                       Ti,Sn)(W,Nb,Ta)[O.sub.4]
  Ilmenorutile         [(Ti,Nb,[Fe.sup.3+]).sub.3]
                       [O.sub.6]
  Ixiolite             [([Fe.sup.2+],[Fe.sup.3+],Ta,Nb,
                       Sc,Ti,Sn,Zr,Mn).sub.4][O.sub.8]
  Manganotantalite     (Mn,Fe)[(Ta,Nb).sub.2][O.sub.6]
  Microlite            [(Ca,Na).sub.2][Ta.sub.2][O.sub.6]
                       (O,OH,F)
  Plumbomicrolite      [(Pb,Ca,U).sub.2][Ta.sub.2]
                       [O.sub.6](OH)
  Pyrochlore           [(Na,Ca).sub.2][Nb.sub.2]
                       [O.sub.6](OH,F)
  Samarskite-(Y)       [(Y,Ce,U,[Fe.sup.3+).sub.3]
                       [(Nb,Ta,Ti).sub.5][O.sub.16]
  Stibiomicrolite      [(Sb,Ca,Na).sub.2]
                       [(Ta,Nb).sub.2][O.sub.7]
  Stibiotantalite      SbTa[O.sub.4]
  Struverite           [(Ti,Ta,[Fe.sup.3+]).sub.3][O.sub.6]
  Uranmicrolite        [(U,Ca,Ce).sub.2][(Ta,Nb).sub.2]
                       [O.sub.6](OH,F)
  Yttrocolumbite-(Y)   (Y,U,[Fe.sup.2+])(Nb,Ta)
                       [O.sub.4]
Phosphates, Vanadates
  Amblygonite          (Li,Na)Al([PO.sub.4]),(F,OH)
  Bermanite            [Mn.sup.2+][[Mn.sup.3+].sub.2]
                       [(P[O.sub.4]).sub.2][(OH).sub.2] .
                       4[H.sub.2]O
  Churchite-(Y)        YP[O.sub.4] . 2[H.sub.2]O
  Clinobisvanite       BiV[O.sub.4]
  Eosphorite           [Mn.sup.2+]Al(P[O.sub.4])
                       [(OH).sub.2] . [H.sub.2]O
  Florencite           (Ce,La,Nd)[Al.sub.3]
                       [(P[O.sub.4]).sub.2][(OH).sub.6]
  Fluorapatite         [Ca.sub.5][(P[O.sub.4]).sub.3] (F,OH)
  Hureaulite           [[Mn.sup.2+].sub.5][(P[O.sub.4]).sub.2]
                       [[P[O.sub.3](OH)].sub.2] . 4[H.sub.2]O
  Hydroxylherderite    CaBe(P[O.sub.4])(OH,F)
  Monazite             (Ce,La,Nd,Th)P[O.sub.4]
  Montebrasite         LiAl(P[O.sub.4])(OH,F)
  Phosphosiderite      [Fe.sup.3+][PO.sub.4] . 2[H.sub.2]O
  Pucherite            BiV[O.sub.4]
  Triplite             [([Mn.sup.2+],[Fe.sup.2+],Mg,Ca).sub.2]
                       (P[O.sub.4])(F,OH)
  Variscite            AlP[O.sub.4] . 2[H.sub.2]O
  Xenotime-(Y)         YP[O.sub.4]


MEMOIRS OF ALTO LIGONIIA [3]

by M. Bettencourt Dias

I had worked in Mozambique during the 1930's and 1940's but during the years of World War II I was kept busy with the exploration and evaluation of gold and graphite deposits which kept me away from Alto Ligonha. As soon as travel became possible again I left Africa for a time and attended the Colorado School of Mines. In 1952 I returned to Alto Ligonha.

My wife Chris and I boarded the Principe Perfeizo, a luxury liner on her return trip from Europe. These ships sailed from Lisbon, went around the African Continent, up to Nacala--the last modem port in Mozambican territory--and then turned around stopping at Beira, Lourenco Marques, Cape Town (in South Africa), Luanda (in Angola), Funchal (the capital of the Island of Madeira) and back to Lisbon. From Lisbon to Lourenco Marques they were always booked solid, but lots of passengers left before the ship stopped in Beira and, since the Geological Survey valued its geologists enough to pay for a first class ticket, I had no trouble getting a berth for the two-day trip to Lourenco Marques.

We were installed in a double-bed cabin with private bath, were served breakfast in bed, spent the daylight hours lounging around a lovely swimming pool and retired to our cabin to dress for dinner, which was served to the accompaniment of a live orchestra and followed by dancing until the wee hours.

The day after we landed in Lourenco Marques I reported to Alexandre Borges at the survey office. All the geologists were in town but most were on vacation and the office was quiet. Borges said that I could turn in my report in two weeks, and then go on a month's vacation before the next field assignment. I asked where I would go next. He answered that Lisbon had lost interest in the uranium of Tete. It had not turned out to be the kind of deposit that the central government could use to show how well they were "developing the colonies." He did not expect that the uranium investigations would continue. We might even be left to ourselves, in which case we might get down to some "honest geological investigations instead of work to satisfy the egos of politicians."

The Director had not yet asked him for suggestions, but when that came to pass he was thinking of proposing the continuation of the geological mapping of the Manica Gold Belt. I handed in my report, titled The Limestone Deposits of the Cheringoma Plateau, long before the end of the two weeks he had given me and then took a vacation. We could not go anywhere for we had no money. So we concentrated on getting our home organized. I assembled bookshelves and kitchen shelves, organized the garage so that it could house the car and assorted trunks and boxes. We did some gardening. Chris trained an African man to maintain the house and to clean and wash our clothes. The month went so fast that I had the impression that the vacation was over a couple of days after it had started.

Back at work the rumors were that Lisbon had indeed lost interest in the "immense mineral wealth" of Mozambique. The geologists and engineers who had come from Lisbon convinced that they could, with their "superior knowledge," make a few trips to the interior and find ore deposits worth millions, had already returned home. I busied myself with the petrographic microscope. It seemed that I was always behind in getting my rock collections ready to be stored in the museum. Borges was very strict making his geologists back up their written reports with collections of rocks and minerals properly classified and accompanied by microscope slides. Only after he had personally checked them were the collections sent to the museum for safekeeping. The museum in Maputo had been founded with the specimens collected in the field before the end of the 19th century by A. A. Freire de Andrade, geologist and mining engineer (who was also the most distinguished Governor General the country had).

We only owned one petrographic microscope, kept in the mezzanine of the mineralogical museum. It was such a prized treasure that it rated an office all to itself while most geologists had to share a cramped space with a colleague. You had to wait your turn to use the microscope.

It soon developed that, although I was an employee of the Geological Survey, I was being "drafted" to go and work for the Alto Ligonha Mining Company. The Company was in difficulty, and 51% of it was owned by the government. So the Governor General was in a position to insist that I go (at twice my usual salary) and try to improve the operations.

Ten days later I flew to Nampula. His Excellency had agreed to a preliminary fact-finding visit of no more than two weeks. There was a car driven by the manager of the mines awaiting my arrival at the airport in Nampula. The trip to the mines took four hours. The only interruption was the crossing of the Ligonha River on a pontoon after passing through Murrupula (from where I had started out on foot to look for Borges, in 1943. See An African Name). After we crossed the river I recognized many of the places where I had then built bridges with local timber and bamboo. They were all made of concrete now. The manager told me that a permanent bridge over the Ligonha, to be located where the pontoon still operated, was already under study.

We arrived at Muiane, the headquarters of the mining company, before dark. The last time I had come this way was nearly ten years ago. That trip from Lourenco Marques to join Borges who was camped at Murrapane, just a few tens of kilometers to the south, had taken two weeks by ship, two days by train, one evening on a Thorneycroft truck, and six days walking with a retinue of nearly three dozen porters through uninhabited jungle. Now, I had done it all in the same day.

Muiane had changed as well. It now had one ample building where the administrative offices were housed; there was a modem hospital; a school house; houses for the employees; a store and a bar; workshops and warehouses occupied one whole side of a street. It looked clean and well taken care of. The mine management had also established a small company museum where they had preserved occasional outstanding mineral specimens. By that time the main sources of revenue for the company were beryl and ferrotantalite; tourmaline was recovered as a by-product from the occasional pockets encountered. I was so impressed by several of the specimens in their little museum that I took them out into the sunlight and photographed them. There were four elbaite specimens, all from the Muiane mine. The first is a slightly divergent parallel crystal group terminated by the pedion. It is a true "watermelon" tourmaline: pink in the middle with a green rind, and measuring about 6 cm tall. The second is a cluster of fractured elbaite crystals, mainly white in color, with a green rind at the base, and measuring 15 cm across. The fractured crystals appear to be partially to almost completely replaced by albite. The third specimen is a typical broken elbaite crystal showing a gem nodule of flawless tourmaline emerging from the center. Usually at Alto Ligonha these are red but I have seen a couple of pale green examples. And the fourth is a perfectly terminated elbaite crystal composed mostly of that rarest of all Mozambican colors: "tea." The tea-colored tourmaline, having a delicate color similar to pale honey or yellowish smoky quartz, was only found at the Muiane mine and was not seen even there after the early 1960's. (See Fig. 28, p. 473.)

The raw production from the various pegmatite mines was delivered by truck to the Muiane plant for upgrading to meet the specifications required by the buyers. Beryl was the most important product. In the 1950's the world production of this mineral was less than one million tons per year with Brazil leading in exports; Nigeria was the second world producer. Either Mozambique, Southwest Africa, or Madagascar usually came third.

The run-of-the-mine beryl was washed with jets of water to remove clay and then dumped on metal-covered tables where it was inspected by pickers of the Achirima and Lomwe tribes; they seemed to have a high natural ability to remove pieces of quartz, felspar, topaz and some lithium minerals that are look-alikes for beryl. Each sorter had a small container in which he saved any gems he found mixed with the run-of-the-mine beryl ore. These were usually tourmaline (green, red, blue, rarely yellow), topaz (blue, white and smoky), aquamarine (sky-blue, rarely deeper shades), kunzite spodumene (light purple), morganite beryl (pink or peach-colored), quartz (transparent, rose-colored, smoky or citrine, rarely amethyst). Bonuses were given to the lucky sorters who found valuable gems (the bonuses were aimed at sharpening their eyes; the question of honesty didn't come into play: both the Achirima, as well as the Lomwe, have very high moral standards and were not in the habit of keeping back stones). Following the sor ting the beryl was dried in the sun and packed in 50-kg bags ready for export to the U.S.A. where it brought about $550 per ton.

Next in economic importance came two very dense, dull-black minerals which occurred in the same zones of the pegmatites that produced beryl. They are members of a mineralogical series which has columbium-rich minerals at one end and grades into tantalum-rich minerals at the other end. Really they should be called columbo-tantalites but are named columbite or tantalite according to the predominant element. [Ed. note: Today the accepted names are ferrocolumbite and ferrotantalite.] Our columbite obtained an average price of approximately $8,500 per ton while our tantalite sold at nearly S23,000 per ton. Both minerals were found in the residues from washing beryl as well as in pockets associated with cassiterite and bismutite in the beryl zone of the pegmatites. They were very dense and similar, except bismutite which was tan in color, while the others were black. Bismutite was hand-picked. The rest was crushed, mixed with water and put over shaking tables to separate the cassiterite from the other two. After d rying, tantalite was separated from columbite because the latter was magnetic enough to be pulled out in a magnetic separator. Each fraction was dried separately and bagged for export in especially heavy-duty bags.

Lithium minerals occurred in the intermediate zones of the pegmatites either by themselves or mixed with beryl, columbium and tantalum minerals, as well as the tourmaline gems of the most beautiful shades of green and red (including the highly priced rubellite). There was a separate shed in which lithium-bearing minerals were processed. Lepidolite (a lavender-colored lithium mica) was so characteristic that it was hand-sorted and shipped in bulk. Spodumene occurred in long, flat, lavender-colored crystals and was easily separated by hand. The residues were washed, checked over for gems, crushed and passed over shaking tables where microlite (another tantalum mineral of very high value), tantalite and bismutite were recovered.

Each section of the plant had an African overseer who moved from place to place issuing advice, showing the other workers how to perform their tasks to his satisfaction and occasionally conducting the singing with gestures like an orchestra conductor. Every task was performed to the rhythm of improvised African songs. Although the system was definitely labor-intensive, one had the impression that every worker knew what he was doing and enjoyed doing it.

The most interesting section was the "mica building." It was apart from the rest of the plant. We entered it through a wide patio with a brick floor where truckloads of bulk mica were piled at regular intervals in heaps of approximately five tons each. Workers wielding pitchforks and shovels attacked the heaps and spread the material into layers of about one foot in thickness which were then hosed with water. The water, loaded with clay and other impurities, ran towards an iron grill where it disappeared to be pumped to the shaking tables for removal of heavy minerals, leaving behind the washed mica which was now shiny and reflected the sunlight like pieces of glass. After it dried in the sun it was loaded into wheelbarrows and carried inside the building where it was spread over a large table from which pickers took the largest "books" of mica to be distributed to the cutters. After the pickers had removed all the good quality mica, the residue was shoveled into wheelbarrows and taken to an enormous pile lo cated under a shed at the back of the patio. This was sold in bulk to be crushed for paints and other uses.

"Cutting" mica is an art that was developed in India (at the time the world's major producer of the commodity). The impurity-free mineral is used as a dielectric substance which reduces the weight of electrical equipment. This is why it has to be cut by hand into sheets about 1 mm thick, taking advantage of the fact that the mineral has perfect cleavage and can be separated into flat sheets of any thickness. The cutters use a sharp knife which is kept fixed while the thin sheet of cleaved mica is pulled against the blade. All impurities, discolorations and inclusions arc removed by the cutters. The final product is graded by type (the most common types were "ruby mica," biotite, muscovite, phlogopite and "black spotted") and by size. It was packed between sheets of Kraft paper inside sturdy handmade wooden boxes. Good, red "ruby mica" of large sizes brought in the 1950's hundreds of dollars per pound.

During the visit I noticed various operations whose efficiency could be improved. The main problem with these operations was their high labor costs. But in Africa one had to think carefully before rushing into mechanization. When you are isolated in the interior, with extremely unreliable communications and transportation; when you have no other electric power than what your generator will produce; when parts for mechanical equipment have to be ordered from representatives that are thousands of miles away and seldom have them in stock; when your fuels and lubricants have to travel weeks on the high seas and more weeks on roads that become impassable for half of the year: you live with the nightmarish fear of what wilt happen to your expensive, highly sophisticated mechanical devices and to your operation should you receive a telegram reading: "REGRET TO INFORM PARTS ORDERED NOT IN STOCK STOP ORDERING TODAY STOP ETA APPROXIMATELY NINETY DAYS."

On the other hand your mining operation is surrounded by villages where the people have no other opportunity to obtain jobs from which they can make enough money to buy clothes and other necessities except by working for you; their children come to study at the mine school; any urgent medical treatment is performed at the mine hospital before they can get to the Government Hospital which is located at the Posto, maybe a couple of days walking distance. Furthermore the tribal people in Mozambique turned out to be excellent workers capable of performing tasks such as sorting and cutting mica far better than any mechanical devices could. Such considerations came out in sharp focus in the beneficiation plant at Muiane.

During the following months I worked at modernizing the Muiane treatment plant and reorganizing the mining operations at many of the pegmatites. It was not uncommon to find amid the concentrates nice crystals of gem minerals, stibiotantalite, microlite, and cassiterite as well as occasional nuggets of native bismuth up to 50 grams in size. The Muiane picking table was a collector's dream.

One of the most striking specimens I saw at Muiane was shown to me on my first visit in 1944. The mine was already famous for excellent gem rubellite and green tourmaline, and was also being worked for ferrotantalite. What they showed me was a very lustrous crystal of stibiotantalite measuring 2.5 x 6 cm and weighing over a pound. At that time it was the largest such crystal in the world, and in addition had real quality going for it, with well-developed basal pinacoid faces and sharp prism and pyramid faces around the sides. The color graded beautifully from colorless to pale beige to honey-yellow and pale brown, with some of the prism-zone faces a rich dark brown. It was later donated to the Freire d'Andrade Museum in Maputo.

A few years later an even larger crystal was found at Muiane, this one measuring 11 cm along one edge and weighing 2 kg (four times the weight of the earlier crystal). It, too, was donated by the mine management to the Andrade Museum, where presumably they are both still preserved.

Stibiotantalite, as I said, was not an uncommon mineral at Muiane, and usually showed up in association with rubellite tourmaline and clusters of cleavelandite albite. At one time I got to wondering whether the Naipa mine about 5 km away might simply be an extension of the same pegmatite, because stibiotantalite was found there, too, usually inside spherical nodules of lepidolite. The ground between the two mines is an uninterrupted mantle of pegmatitic regolith, and prospecting pits which were sunk along the trace connecting the two mines found abundant eluvial ferrotantalite.

One day I received instructions to have a road cut through the jungle so that cars could reach the old abandoned Nahia mine. I recruited a crew composed of a few dozen local tribesmen and we set to work. The men, equipped with bush knives, axes, picks and hoes, cleared a path wide enough for a truck, and smoothed it over by removing rocks and stumps here and there as necessary. Big trees and large boulders we went around, so the road was not exactly straight.

The scouting group that checked the ground ahead for obstacles was led by an old tribesman who knew (more or less) where the abandoned mine was. When we were getting close to our goal, one of the scouts came back to see me where I was working with the "engineering brigade." He was excited, and wanted me to come and see a strange sight they had come upon: "large pieces of water rock sticking out of the ground." This phenomenon, he said, was right in the path of the road, and the old tribesman leading the scouts wanted to know whether we wanted to remove the obstacles or curve the road around them.

I followed the scout and came to a clearing where the ground was littered with broken chunks of transparent quartz of all sizes, as well as five magnificent crystals of quartz, almost as tall as I am, protruding from the earth! One of them, standing vertically, was totally water-clear and a pale amber color. The others were milky to partly transparent and leaned at various angles. They were all well-formed and terminated, weighting perhaps three-quarters of a ton each.

I learned that the local language (Achirima) did not have words for "quartz," "transparent," "smoky color," or "crystal," so they had just done the best they could in describing the crystals as "water rock." This description seemed appropriate and sensible to me, so I adopted the term from then on.

Ultimately I concluded that the remarkable forest of quartz crystals was the exposed quartz core of a large pegmatite, perhaps even an extension of the nearby Nahia pegmatite. I ordered the road to be driven in a wide loop around the occurrence and had it cleared of underbrush. I instructed the men stemly not to take away any specimens--not that they would have considered such foolishness anyway; only white men are crazy enough to collect rocks!

The quartz crystal outcrop was later threatened when the mine came under new ownership. The new owners devised a scheme for getting the rough mine road I had built improved at no cost to themselves: they donated the crystals to the Geographic Society of Lisbon. The catch was that the Society had to come get them, and that meant the Society would be forced to invest in a program of road building. The project was begun, but the Society ran out of money halfway before reaching the crystals, and abandoned the project. They never did take the crystals away; as far as I know, they are still where we found them.

At the time I worked there the Alto Ligonha Pegmatite District was only known to a few serious collectors of rare minerals. Its rubellite was highly prized (and already highly priced) by gem cutters at Idar-Oberstein and in the Far East. Very few people in the United States had heard of the district. Cut stones, especially those from the Muiane mine, were sold as Brazilian because buyers associated beautiful tourmaline, aquamarine and morganite with that country. The sellers could charge more by letting the buyers think that way.

I remember some geologists who, even after they had visited the mines and seen what they were producing, insisted on telling me that only Brazil could be considered as a serious producer of beryl, columbite and tantalite. From a few to whom I tried to convey the idea of the enormous potential of the field, I received looks of disbelief and veiled remarks about the dangers of being in the bush too long! But at least three visitors understood what I was saying. Martin L. Ehrmann (see Smith and Smith, 1994) of California, who visited the mines in 1955, became a regular purchaser of stones and specimens; Dr. E. N. Cameron tried to interest a large American corporation to invest in exploration and development and sent two geologists to study the alluvial deposits of columbite-tantalite; Dr. Erland Grip, chief geologist of the Boliden Mining company, of Boliden, Sweden, spent some time with me in the field and later sent a group of representatives of his company to investigate the possibilities of investment in Mo zambique. But when they contacted the directors of the Alto Ligonha Company to discuss the formation of joint ventures to develop the district, they found not the faintest interest. Any association with large companies made the directors suspicious of being replaced by competent management. And that they did not want.

When the so-called "independence" took place under the Marxists in 1975, I knew that my days were numbered. I sold my mineral collection to a South African dealer before the government could get around to confiscating it. Then I went around to small post offices where I was not known and mailed off in many small packages what I had left (mostly gem rough) to the Colorado School of Mines; I did not give a sender's name or return address, hoping that the School would guess the packages were from an alumnus on the run. About half of the packages got through, and the School lived up to my hopes, saving everything for me until I showed up to claim it. Arriving in Colorado at the age of 55, with only $100 in my pocket, I was grateful to find that cutting material waiting for me.
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Author:Dias, Manuel Bettencourt; Wilson, Wendell E.
Publication:The Mineralogical Record
Article Type:Statistical Data Included
Geographic Code:6MOZA
Date:Nov 1, 2000
Words:16224
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