Sperrylite is a rare and dense platinum arsenide mineral primarily found in magmatic nickel-copper deposits. It typically forms metallic, brilliant silver-white crystals that look superficially similar to pyrite but are significantly heavier. Collectors prize it as the most important mineral source of platinum.
Is this sperrylite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch sperrylite with a known reference. Sperrylite sits at Mohs 6-7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: tin white.
- 5Look at form & habitCrystal system: cubic. Typical habit: crystalline, disseminated.
Often confused with
Sperrylite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Sperrylite leaves black, Pyrite leaves greenish black to brownish black.
How to tell apart: Streak differs, so Sperrylite leaves black, Cobaltite leaves grayish black.
Often found alongside sperrylite
Minerals reported to co-occur with sperrylite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- PtAs₂
- Mohs hardness
- 6-7
- Density
- 10.58 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Crystalline, disseminated
- Cleavage
- Indistinct on {001}
- Rarity
- Uncommon
- Uses
- Collector, Ore of platinum
- Host rock
- The most widespread platinum mineral, occurring in every type of deposit
Where rockhounds find sperrylite
Classic worldwide localities
- New Rambler Cu–Ni mine, Medicine Bow Mountains, east of Encampment, Albany Co., Wyoming, USA
- Key West mine, east of Moapa, Bunkerville district, Clark Co., Nevada, USA
- Stillwater complex, Montana, USA
- Vermilion (type locality), Victoria, and Frood mines, Algoma district, near Sudbury, Ontario, Canada
- Bushveld complex, on the Merensky reef, Transvaal, South Africa, Tweefontein Farm, near Potgietersrus
- Atok, Onverwacht, and Rustenburg mines
Field-hunting tip
Where it forms: The most widespread platinum mineral, occurring in every type of deposit. If you start seeing pyrrhotite, pentlandite, chalcopyrite in float, you are in the right ground. Typical habit: crystalline, disseminated. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify sperrylite?+
Where is sperrylite found?+
Is sperrylite safe to handle?+
What rocks look like sperrylite?+
What minerals are found with sperrylite?+
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What is sperrylite used for?+
Find sperrylite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
