Cobaltomenite is a rare hydrated cobalt selenite mineral that forms stunning rose-red to pink acicular or fibrous crystals. It is primarily found as a secondary mineral in oxidized zones of selenium-rich hydrothermal ore deposits.
Is this cobaltomenite?
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 cobaltomenite with a known reference. Cobaltomenite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: dark pink.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: dark red, pink.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular crystals, crusts, or radial aggregates.
Often confused with
Cobaltomenite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Cobaltomenite leaves dark pink, Erythrite leaves pale red to pink; luster reads vitreous on Cobaltomenite and subadamantine, pearly on cleavages on Erythrite.
How to tell apart: Streak differs, so Cobaltomenite leaves dark pink, Chalcomenite leaves light blue.
Often found alongside cobaltomenite
Minerals reported to co-occur with cobaltomenite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CoSeO₃·2H₂O
- Mohs hardness
- 2.5
- Density
- 3.42 g/cm³
- Streak
- Dark pink
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular crystals, crusts, or radial aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral in the oxidation zone of hydrothermal selenium-sulfide-bearing vein deposits
Where rockhounds find cobaltomenite
Classic worldwide localities
- A.E.C. No. 8 mine, Temple Mountain, Emery Co., and at the Parco mine group, Thompson district, Grand Co., Utah, USA
- Cerro de Cacheuta, Mendoza Province, Argentina
- El Dragón mine, 30 km southwest of Cerro Rico de Potosí, Potosí, and in the Pacajake mine, Hiaco, 30 km east-northeast of Colquechaca, Potosí, Bolivia
- Musonoi and Kambove West mines, Shaba Province, Congo (Zaire)
Field-hunting tip
Where it forms: A secondary mineral in the oxidation zone of hydrothermal selenium-sulfide-bearing vein deposits. If you start seeing chalcomenite, molybdomenite, clinochalcomenite in float, you are in the right ground. Typical habit: acicular crystals, crusts, or radial aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cobaltomenite?+
Where is cobaltomenite found?+
Is cobaltomenite safe to handle?+
What rocks look like cobaltomenite?+
What minerals are found with cobaltomenite?+
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Find cobaltomenite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
