The Pacajake mine, hidden high in the Cordillera Oriental of the Bolivian Andes, is famous for its rare selenides, selenates and selenites, and is the type locality for penroseite, ahlfeldite, olsacherite and mandarinoite.
Some favored penroseite, as first proposed by Samuel Gordon of Philadelphia in 1925, based on his description of impure material from a purchased sample of unknown provenance (and later corroborated by the British Museum); others favored the name blockite, as proposed for pure material collected at the Pacajake mine by the Germans working in Bolivia.
It was during this time, in 1925, that Samuel Gordon obtained the sample of the material which he named penroseite; the specimen was in a collection of minerals which he bought in the nearby mining camp of Colquechaca (Gordon, 1925).
The selenides included mainly the nickel selenide penroseite, intimately mixed with selenides of lead (clausthalite), silver (naumannite) and mercury (tiemannite).
Assays have shown the selenides from the West Vein to be dominated by penroseite and to include clausthalite, tiemannite and naumannite with possible krutaite (although the Cu may be chalcopyrite).
Herzenberg and Ahlfeld (1935) described it as occurring on specimens of penroseite as a transparent red-brown mineral, with a strong luster, in a lobe form in fractures in penroseite.
Ahlfeldite is rare, occurring on only a few samples as an alteration product of penroseite in crystalline crusts 1 to 1.5 mm thick covering areas of only a few square millimeters or filling small cavities.
The Shinkolobwe mine has yielded cattierite, carrollite, linnaeite, penroseite, siegenite, comblainite, oursinite and heterogenite (3R).
In the lower part of the Shinkolobwe oxidation zone, siegenite rich in selenium is also found, in close association with penroseite (described below).
Penroseite and the associated sulfides form mixed clusters measuring up to several [cm.sup.3] within a gray vuggy dolomite rich in microcrystals of barite and anhydrite.
Katanga Crescent Outside of Stratiform Vein-like Katanga Cresent Cobalt Cobalt Cobalt Deposits Deposits(*) Deposits(**) Primary Linnaeite Linnaeite Linnaeite Minerals Carrollite Carrollite Carrollite Cattierite Cobaltite Siegenite Trogtalite Penroseite Secondary Heterogenite-3R Heterogenite-3R Heterogenite-3R Minerals Heterogenite-2H Oursinite Kolwezite Comblainite Sphaerocobaltite Cobaltomenite Julienite * Shinkolobwe ** Kipushi Sphaerocobaltite COC[O.sub.3]
(1975) Replacement partiel du selenium par le soufre dans la penroseite (Ni,Co,Cu)[(Se,S).sub.2] de Shinkolobwe (Zaire).