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 7.5-8 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Cochromite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Cochromite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: cubic. Typical habit: octahedral crystals, massive.
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 7.5-8 vs. 5.5); streak differs — Cochromite leaves black, Chromite leaves dark brown; luster reads metallic on Cochromite and submetallic on Chromite.
How to tell apart: Cochromite is noticeably harder (Mohs 7.5-8 vs. 5.5-6.5).
How to tell apart: Streak differs — Cochromite leaves black, Spinel leaves white; luster reads metallic on Cochromite and vitreous 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
- (Co,Ni,Fe,Mn)(Cr,Al)₂O₄
- Mohs hardness
- 7.5-8
- Density
- 4.6-4.8 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Octahedral Crystals, Massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Ultramafic Rocks, Serpentinites
- Typical price
- $50-500 depending on specimen quality
Where rockhounds find cochromite
Classic worldwide localities
- Bou Azzer district, Morocco
- Kambalda, Australia
Field-hunting tip
Look in ultramafic rocks, serpentinites country — that is the host setting where cochromite typically forms. If you start seeing chromite, serpentine, cobaltite in float, you are in the right ground. Field specimens usually show a octahedral crystals, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find cochromite on the map
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