Mineral of the Month: SPERRYLITE - PtAs2

By Dr. Ray Grant and Chris Whitney-Smith

The mineral of the month for March is Sperrylite, platinum arsenide, PtAs2. It is cubic and usually well crystallized as cubes and cubo-octahedrons. The color is tin-white and the streak is black. The hardness is 6-7. The color, the crystals, and the weight (high specific gravity) are the best ways to identify it.

Sperrylite is the most common platinum mineral and found in many different types of deposits. Some of the best specimens are from South Africa and Russia. In Arizona, platinum is a rare element, there are reports of it, but most have been scams and no platinum minerals have been officially described from Arizona.

Show & Tell or Just Show: Members are invited to bring (ONE) sample from their collection of the mineral of the month and give a brief story about where they collected it or something about the specimen.

Unknown minerals for identification can still be brought to the meetings.

PHOTO CAPTION

SPERRYLITE PtAs2, Chalcopyrite (brassy) CuFeS2, 2.3cm, Talnakh, Norilsk, Siberia, Krasnoyarsky Kray, Russia. Spirifer Minerals Collection, Jeff Scovil Photo.

SPERRYLITE PtAs2, Chalcopyrite (brassy) CuFeS2, 5.6cm, Talnakh Cu-Ni deposit, Norilsk, East Siberia, Krasnoyarsky Kray, Russia. Rice NW Museum Collection, Jeff Scovil Photo.