Almeidaite

almeidaite

xenotime-(Y)

bastnasite-(La)

anatase

Images

Formula: PbZn2(Mn,Y)(Ti,Fe3+)18O36(OH,O)2
Valence: Pb2+Zn2+2(Mn2+,Y)(Ti4+,Fe3+)18O36(OH,O)2
Oxide of lead, zinc, manganese, yttrium, titanium and ferric iron, crichtonite group
Crystal system: Trigonal
Specific gravity: 4.68 measured, 4.616 calculated
Hardness: 6
Streak: Brown
Colour: Black; metamict due to trace thorium
Luminescence: Not fluorescent under either long wave or short wave UV
Common impurities: Fe,Y,Sr,(Ca,La)
Environments

Hydrothermal environments

Localities

At the type locality, Paulo de Mudo claim, Novo Horizonte, Bahia, Brazil, almeidaite occurs in association with quartz, rutile, anatase, hematite, kaolinite, muscovite, xenotime-(Y) and bastnäsite-(La). Almeidaite forms isolated, black, opaque, sub-metallic, platy crystals, up to 30 mm × 30 mm × 6 mm in size. Most of the crystals are multiply twinned (MM 79.2.269-283).
The almeidaite occurs in altered dacite 2 meters from a hydrothermal quartz vein (HOM).
Almeidaite from Paulo de Mudo claim - Image

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