Chalcocyanite is a rare anhydrous copper sulfate that typically forms as a dehydration product of chalcanthite. It appears as pale blue crusts or powdery aggregates and is notably unstable in humid environments, as it easily absorbs water to revert to chalcanthite.
Is this chalcocyanite?
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 chalcocyanite with a known reference. Chalcocyanite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: blue, brown, green, yellow, yellow brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: crusts, fibrous aggregates, massive.
Often confused with
Chalcocyanite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside chalcocyanite
Minerals reported to co-occur with chalcocyanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuSO₄
- Mohs hardness
- 3.5
- Density
- 3.65 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Crusts, fibrous aggregates, massive
- Cleavage
- Poor
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As sublimates near volcanic fumaroles
Where rockhounds find chalcocyanite
Classic worldwide localities
- Mount Vesuvius, Campania, Italy
- Tolbachik fissure volcano, Kamchatka Peninsula, Russia
- Izalco volcano, El Salvador
Field-hunting tip
Where it forms: As sublimates near volcanic fumaroles. If you start seeing dolerophanite, melanothallite, eriochalcite in float, you are in the right ground. Typical habit: crusts, fibrous aggregates, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify chalcocyanite?+
Where is chalcocyanite found?+
Is chalcocyanite safe to handle?+
What rocks look like chalcocyanite?+
What minerals are found with chalcocyanite?+
What kind of rock does chalcocyanite form in?+
What is chalcocyanite used for?+
Find chalcocyanite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
