Erlichmanite is a rare osmium sulfide mineral usually found as microscopic grains in platinum-group mineral assemblages. It typically occurs in ultramafic rocks or heavy mineral placer deposits, identified by its metallic luster and high specific gravity.
Is this erlichmanite?
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 erlichmanite with a known reference. Erlichmanite sits at Mohs 4.5-5.5, 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: gray white.
- 5Look at form & habitCrystal system: cubic. Typical habit: small cubes and octahedra, granular.
Often confused with
Erlichmanite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Laurite is the harder of the two (Mohs 7.5 vs. 4.5-5.5); streak differs, so Erlichmanite leaves black, Laurite leaves dark gray.
How to tell apart: Streak differs, so Erlichmanite leaves black, Pyrite leaves greenish black to brownish black.
Often found alongside erlichmanite
Minerals reported to co-occur with erlichmanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- OsS₂
- Mohs hardness
- 4.5-5.5
- Density
- 8.28 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Small cubes and octahedra, granular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Research
- Host rock
- Typically in PGM placers, likely derived from chromitites associated with ophiolites and other Alaskan-type ultramafic complexes
Where rockhounds find erlichmanite
Classic worldwide localities
- A placer at the MacIntosh mine, Willow Creek, Trinity River, Humboldt Co. (type locality), and in gravels from the American River, Sacramento Co., California, USA
- Salmon River placers, Goodnews Bay, Alaska, USA
- Placers on the Tulameen River, British Columbia, Canada
- Ural Mountain placers, Siberia, and in the Konder massif, Aldan Shield, Sakha, Russia
- A platinum metal nugget from Joubdo stream, Birbir River, Ethiopia
- Placers at Guma Water, Sierra Leone
Field-hunting tip
Where it forms: Typically in PGM placers, likely derived from chromitites associated with ophiolites and other Alaskan-type ultramafic complexes. If you start seeing pt–fe alloy, platinum, osmium in float, you are in the right ground. Typical habit: small cubes and octahedra, granular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify erlichmanite?+
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What rocks look like erlichmanite?+
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Find erlichmanite on the map
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