El Peñón pegmatite, El Quemado District, Nevados de Palermo, Salta, Argentina

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This pegmatite main minerals are quartz, plagioclase, microcline, to which is added Spodumene, Muscovite, Biotite, Beryl, Lepidolite, Tourmaline, Sphalerite, Molybdenite, Uraninite, Niobite, Tantalite, Native Bismuth, Bismuthinite, Ferrotapiolite, Manganotantalite, Microlite, Uranomicrolite, Bismuthmicrolite, Hafniferous Zircon, Triplite, Montebrasite and other phosphates and uranium oxide minerals.
Minerals of the columbite group have varying compositions: from Ferrocolumbite to Manganocolumbite and the less evolved pegmatites and Shales to Manganotantalite in "El Peñon". In this case, Microlite, Uranomicrolite, and occasionally Bismuth-Microlite often accompany the most advanced members. Ferrocolumbite was determined by chemistry and x-ray diffraction.
The crystals are centimetric to millimetric, tabular, sub to euhedrales, with development of forms {010}, {100}, {110}, {130}, {011}, {111} in different combinations. Found in the intermediate areas, including in plagioclase, microcline or primary phosphates. Alluvial crystals are prismatic or tabular thicknesses and often have vertical striations. They are black, fragile and have metallic sheen to submetallic.
Brazilianite: found in the intermediate zone of the "El Peñon" pegmatite crystals no larger than 2 mm implanted on a prismatic face of an individual of Quartz.

Mineral List

Albite Amblygonite 'Apatite' Arrojadite-(KFe) Bederite (TL) Beryl

Bismuth Bismuthinite Brazilianite 'Columbite' Eosphorite Fairfieldite

Heterosite ? Ixiolite Laueite Microlite Group Muscovite Schorl

'Tourmaline' Triphylite Uraninite Ushkovite Zircon

23 entries listed. 20 valid minerals. 1 type locality (valid mineral).