Osarsite is a rare platinum-group mineral typically occurring as microscopic inclusions within chromite deposits. It is recognized by its metallic luster and is usually identified via electron microprobe analysis rather than visual inspection in the field due to its minuscule size.
Is this osarsite?
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 osarsite with a known reference. Osarsite sits at Mohs 6, 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.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: intergrown crystals.
Often confused with
Osarsite 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. 6); streak differs, so Osarsite leaves black, Laurite leaves dark gray.
How to tell apart: Streak differs, so Osarsite leaves black, Hollingworthite leaves grayish-black.
Often found alongside osarsite
Minerals reported to co-occur with osarsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Os(AsS)
- Mohs hardness
- 6
- Density
- 8.44 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Intergrown crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- In a platinum-bearing sample of placer sand (Gold Bluff, California, USA)
Where rockhounds find osarsite
Classic worldwide localities
- Gold Bluff, Humboldt Co., California, USA (type locality), and in the Salmon River placers, Goodnews Bay, Alaska, USA
- Zlatoust, Ural Mountains, Russia
- Kola Peninsula, Russia
- Neozhidannyy Creek placers, Tuva, Russia
- Witwatersrand, Transvaal, South Africa
- Anduo, Tibet, China
Field-hunting tip
Where it forms: In a platinum-bearing sample of placer sand (Gold Bluff, California, USA). If you start seeing irarsite, ruthenarsenite, sperrylite in float, you are in the right ground. Typical habit: intergrown crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify osarsite?+
Where is osarsite found?+
Is osarsite safe to handle?+
What rocks look like osarsite?+
What minerals are found with osarsite?+
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What is osarsite used for?+
Find osarsite on the map
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