Penroseite Locality: Virgen de Surumi mine (Pacajake mine; Pakajake mine), Pakajake Canyon (Pacajake Canyon), Chayanta Province , Potosí Department , Bolivia ( Locality at mindat.org ) Size: 4.9 x 2.4 x 1.8 cm. Penroseite is a very rare nickel, cobalt, copper selenide and this rich and fine specimen is from the Type Locality - the Virgen de Surumi Mine of Bolivia. The famous selenium minerals from this locality have often been falsely attributed to the Hiaco mine (2km west, on the opposite flank of Pakajake canyon) or to the Colquechaca mine (28km southwest), but neither of those mines yields any selenium minerals at all. Silvery, metallic, parallel-growth blades of penroseite comprise nearly all of this very rich specimen. Accompanied by a 1950s era, faded Burminco label that has a penciled-in, August, 1951 date. Ex. Mullane Collection. Weighs 60 grams. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Penroseite
A rare nickel-cobalt-copper selenide discovered in 1925 in a Bolivian rhyolite.
Intro adapted from Wikipedia (CC BY-SA).
Penroseite is an IMA-recognized mineral species in the sulfide class, with the chemical formula (Ni,Co,Cu)Se₂.
It crystallizes in the cubic crystal system (space group Pa3). It is a member of the Pyrite structural group.
Key properties: Mohs hardness 2.5–3; specific gravity 6.58–6.74; Black streak; Metallic, tarnishes rapidly. R: (400) 40.2, (420) 40.1, (440) 40.1, (460) 40.2, (480) 40.4, (500) 40.7, (520) 41.1 luster.
IMA symbol Pen, grandfathered status — known before the IMA’s founding, named in 1926.
Found in hydrothermal veins.
It is found associated with Naumannite, clausthalite, gersdorffite, tiemannite, pyrite, chalcopyrite (Pacajake mine, Bolivia); clausthalite, sederholmite, trüstedtite (Kuusamo, Finland).
In honor of Dr. Richard Alexander Fullerton Penrose, Jr. (1863–1931), American economic geologist, of Philadelphia, Pennsylvania, USA.