SPERRYLITE

    Class : Sulfides and sulfosalts
    Subclass : Arsenides
    Crystal system : Cubic
    Chemistry : PtAs2
    Rarity : Rare to very rare

Sperrylite is, with native platinum, one of the rare platinum minerals to form samples of macroscopic size. This platinum arsenide is found, like platinum, in deposits related to ultrabasic rocks and in the alluvium derived from them; in its primary deposits, it is associated with platinum, chromite, pentlandite, pyrrhotite and other platinum minerals. Unlike platinum, and because of its association with arsenic, this mineral is brittle and very hard (6 to 7). It was named in honor of Francis Louis Sperry, a chemist in Sudbury (Canada), who discovered the mineral. Sperrylite has a strong metallic luster and a pewter-white color; It occurs in cubo-octahedral crystals (sometimes rounded by the presence of many faces), frequently included in other sulfides. It is an important ore of platinum.

Main photo : Sperrylite on chalcopyrite from Talnakh, Russia © Rice Northwest Museum of Rocks and Minerals

Sperrylite on chalcopyrite from Talnakh, Russia © Rob Lavinsky
Sperrylite from Broken Hammer, Ontario, Canada © Stephan Wolfsried
Sperrylite from Broken Hammer, Ontario, Canada © John A. Jaszczak
Sperrylite from Broken Hammer, Ontario, Canada © John R. Montgomery

Sperrylite in the World

Sperrylite crystals can exceptionally exceed 4 cm, notably in the Talnakh deposit (Norilsk district, Russia). It is also known in centimetric crystals in the Vermilion mine near Sudbury (Canada), its type locality. The most famous district for the quality of its samples is however that of Pietersburg (Transvaal, South Africa) with the mines of Merensky Reef : it is in this district that the most beautiful crystal known to date was discovered in 1924 (35 mm by 19 mm).

Sperrylite in France

In France, sperrylite is reported in the sediments of the Marcieux quarry near Chambéry (Savoie), as well as in the alluvium of Belley (Ain).

Twinning

No twinning known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 6 to 7
Density : 10.58
Fracture : Conchoidal
Streak : Dark gray to black

TP : Opaque
RI : -
Birefringence : 0
Optical character : None
Pleochroism : None
Fluorescence : None

Solubility : -

Magnetism : NoneRadioactivity : None