Iridarsenite is a very rare platinum-group mineral typically occurring as microscopic anhedral grains in platinum-group element deposits. It is most frequently identified in polished sections during ore microscopy due to its extremely small grain size and association with other platinum-group minerals.
Is this iridarsenite?
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 iridarsenite with a known reference. Iridarsenite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Iridarsenite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Iridarsenite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: silver-white.
- 5Look at form & habitCrystal system: cubic. Typical habit: anhedral grains.
Often confused with
Iridarsenite 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. 3.5).
How to tell apart: Hollingworthite is the harder of the two (Mohs 6 vs. 3.5); streak differs — Iridarsenite leaves black, Hollingworthite leaves grayish-black.
Often found alongside iridarsenite
Minerals reported to co-occur with iridarsenite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ir,Pt)As₂
- Mohs hardness
- 3.5
- Density
- 11.6 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Anhedral Grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Ultramafic Igneous Rocks
- Typical price
- $100-500 per specimen
Where rockhounds find iridarsenite
Classic worldwide localities
- Itabira, Brazil
- Bushveld Complex, South Africa
- Stillwater Complex, USA
Field-hunting tip
Look in ultramafic igneous rocks country — that is the host setting where iridarsenite typically forms. If you start seeing platinum, palladium, chromite in float, you are in the right ground. Field specimens usually show a anhedral grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find iridarsenite on the map
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