Chalcomenite is a rare copper selenite mineral that forms striking bright blue, prismatic crystals. It is typically found as a secondary mineral in the oxidation zones of selenium-rich ore deposits, often appearing as crusts or small crystal clusters.
Is this chalcomenite?
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 chalcomenite with a known reference. Chalcomenite 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. Chalcomenite leaves a pale blue streak.
- 3Read the lusterHold the specimen under a strong light. Chalcomenite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: blue, blue-green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: short prismatic crystals, crusts, radial aggregates.
Often confused with
Chalcomenite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Azurite is the harder of the two (Mohs 3.5-4 vs. 2.5); streak differs — Chalcomenite leaves pale blue, Azurite leaves light blue; luster reads vitreous on Chalcomenite and vitreous to dull on Azurite.
How to tell apart: Streak differs — Chalcomenite leaves pale blue, Chalcanthite leaves white.
Often found alongside chalcomenite
Minerals reported to co-occur with chalcomenite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuSeO₃·2H₂O
- Mohs hardness
- 2.5
- Density
- 3.32 g/cm³
- Colors
- Streak
- Pale Blue
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Short Prismatic Crystals, Crusts, Radial Aggregates
- Cleavage
- Perfect On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Hydrothermal Selenium-bearing Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find chalcomenite
Classic worldwide localities
- Sierra de Cacheuta, Argentina
- Hope's Nose, England
- Goldfield, Nevada, USA
- Skouriotissa, Cyprus
Field-hunting tip
Look in oxidized zones of hydrothermal selenium-bearing deposits country — that is the host setting where chalcomenite typically forms. If you start seeing kerstenite, coquimbite, molybdomenite in float, you are in the right ground. Field specimens usually show a short prismatic crystals, crusts, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find chalcomenite on the map
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