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: monoclinic. 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, so 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
- Monoclinic
- Crystal habit
- Anhedral Grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Ultramafic Igneous Rocks
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, 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
How do you identify iridarsenite?+
Where is iridarsenite found?+
Is iridarsenite safe to handle?+
What rocks look like iridarsenite?+
What minerals are found with iridarsenite?+
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Find iridarsenite on the map
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