Zincochromite is an exceptionally rare member of the spinel group where zinc replaces iron or magnesium. Collectors typically find it as dark, granular masses within ultramafic environments or specific hydrothermal ore deposits. Due to its scarcity and similarity to more common chromites, positive identification usually requires professional mineralogical analysis.
Is this zincochromite?
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 zincochromite with a known reference. Zincochromite sits at Mohs 5.8, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: semimetallic.
- 4Match the color rangeCompare against the expected color range: brownish black.
- 5Look at form & habitCrystal system: cubic. Typical habit: euhedral crystals.
Often confused with
Zincochromite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads semimetallic on Zincochromite and metallic to submetallic on Chromite.
How to tell apart: Streak differs, so Zincochromite leaves brown, Magnetite leaves black; luster reads semimetallic on Zincochromite and metallic to submetallic, may be dull on Magnetite.
How to tell apart: Gahnite is the harder of the two (Mohs 7.5-8 vs. 5.8); streak differs, so Zincochromite leaves brown, Gahnite leaves gray; luster reads semimetallic on Zincochromite and vitreous on Gahnite.
Often found alongside zincochromite
Minerals reported to co-occur with zincochromite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- ZnCr₂O₄
- Mohs hardness
- 5.8
- Density
- 5.434 g/cm³
- Colors
- Streak
- Brown
- Luster
- Semimetallic
- Transparency
- Opaque, translucent in thin slivers
- Crystal system
- Cubic
- Crystal habit
- Euhedral crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Replacing chromian aegirine in micaceous metasomatites
Where rockhounds find zincochromite
Classic worldwide localities
- Velikaya Guba uranium deposit, near Onega Lake, Padma, Zaonezhskii Peninsula, southern Karelia, Russia
Field-hunting tip
Where it forms: Replacing chromian aegirine in micaceous metasomatites. If you start seeing quartz, chromian aegirine in float, you are in the right ground. Typical habit: euhedral crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify zincochromite?+
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Find zincochromite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
