Cochromite is an extremely rare member of the spinel group where cobalt is a dominant cation. It typically occurs as small, opaque, black octahedral grains within serpentinized ultramafic rock environments. Collectors often identify it by its specific association with cobalt-rich ores in hydrothermal veins.
Is this cochromite?
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 cochromite with a known reference. Cochromite sits at Mohs 7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: greenish gray.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: cubic. Typical habit: granular.
Often confused with
Cochromite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Cochromite is noticeably harder (Mohs 7 vs. 5.5); streak differs, so Cochromite leaves greenish gray, Chromite leaves brown.
How to tell apart: Streak differs, so Cochromite leaves greenish gray, Magnetite leaves black.
How to tell apart: Streak differs, so Cochromite leaves greenish gray, Spinel leaves white; luster reads metallic on Cochromite and vitreous, splendent to dull on Spinel.
Often found alongside cochromite
Minerals reported to co-occur with cochromite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CoCr₂O₄
- Mohs hardness
- 7
- Density
- 5.22 g/cm³
- Colors
- Streak
- Greenish gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Granular
- Cleavage
- Indistinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Replacing chromite in a small tabular nickel deposit at the contact between quartzite and serpentinized ultramafics
Where rockhounds find cochromite
Classic worldwide localities
- Bon Accord deposit, Barberton, Transvaal, South Africa
- Bo Phloi, 40 km north of Kanchanaburi, Thailand
Field-hunting tip
Where it forms: Replacing chromite in a small tabular nickel deposit at the contact between quartzite and serpentinized ultramafics. If you start seeing trevorite, nichromite, liebenbergite in float, you are in the right ground. Typical habit: granular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cochromite?+
Where is cochromite found?+
Is cochromite safe to handle?+
What rocks look like cochromite?+
What minerals are found with cochromite?+
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What is cochromite used for?+
Find cochromite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
