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. Cobaltomenite leaves a pink streak.
- 3Read the lusterHold the specimen under a strong light. Cobaltomenite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: rose-red, pink, violet-red.
- 5Look at form & habitCrystal system: orthorhombic. 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 — Cobaltomenite leaves pink, Erythrite leaves pale pink; luster reads vitreous on Cobaltomenite and adamantine to pearly on Erythrite.
How to tell apart: Streak differs — Cobaltomenite leaves pink, Chalcomenite leaves pale 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
- 3.3-3.4 g/cm³
- Colors
- Streak
- Pink
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular Crystals, Crusts, Or Radial Aggregates
- Cleavage
- Distinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Hydrothermal Selenium-bearing Ore Deposits
- Typical price
- $50-500 thumbnail
Where rockhounds find cobaltomenite
Classic worldwide localities
- Sierra de Cacheuta, Argentina
- Goldfield, Nevada, USA
- Musonoi Mine, DR Congo
- Trogtal Quarry, Germany
Field-hunting tip
Look in oxidized hydrothermal selenium-bearing ore deposits country — that is the host setting where cobaltomenite typically forms. If you start seeing chalcomenite, erythrite, klockmannite in float, you are in the right ground. Field specimens usually show a acicular crystals, crusts, or radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cobaltomenite?+
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Find cobaltomenite on the map
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