Cooperite is a rare platinum sulfide mineral typically occurring as microscopic inclusions within magmatic sulfide deposits. Collectors prize it as one of the primary ore minerals for platinum, usually appearing as dull metallic grains in matrix rock.
Is this cooperite?
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 cooperite with a known reference. Cooperite sits at Mohs 4-5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Cooperite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Cooperite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: white, lead-gray.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: irregular grains, small prismatic crystals.
Often confused with
Cooperite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Sperrylite is the harder of the two (Mohs 6-7 vs. 4-5).
How to tell apart: Laurite is the harder of the two (Mohs 7-7.5 vs. 4-5).
How to tell apart: Pyrite is the harder of the two (Mohs 6-6.5 vs. 4-5); streak differs — Cooperite leaves black, Pyrite leaves greenish-black to brownish-black.
Often found alongside cooperite
Minerals reported to co-occur with cooperite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- PtS
- Mohs hardness
- 4-5
- Density
- 8.9-9.1 g/cm³
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Tetragonal
- Crystal habit
- Irregular Grains, Small Prismatic Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Mafic and Ultramafic Igneous Complexes
- Typical price
- $50-300 per specimen
Where rockhounds find cooperite
Classic worldwide localities
- Bushveld Complex, South Africa
- Sudbury, Canada
- Stillwater Complex, USA
- Norilsk, Russia
Field-hunting tip
Look in mafic and ultramafic igneous complexes country — that is the host setting where cooperite typically forms. If you start seeing sperrylite, laurite, chalcopyrite in float, you are in the right ground. Field specimens usually show a irregular grains, small prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find cooperite on the map
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