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.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrare

Chalcocyanite

Hardness: 2.5
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this chalcocyanite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch chalcocyanite with a known reference. Chalcocyanite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Chalcocyanite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Chalcocyanite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: blue, pale blue.
5
Look at form & habit
Crystal 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.

How to tell apart: Brochantite is the harder of the two (Mohs 3.5-4 vs. 2.5); streak differs — Chalcocyanite leaves white, Brochantite leaves pale-green.

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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: 2.5
Density: 3.2 g/cm³
Colors: Blue Pale Blue
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Crusts, Fibrous Aggregates, Massive
Cleavage: Poor
Rarity: Rare
Uses: Collector
Host rock: Fumaroles and Oxidized Copper Deposits
Typical price: $50-300 per specimen

Where rockhounds find chalcocyanite

Classic worldwide localities

Vesuvius, Italy
Chuquicamata, Chile
Rio Tinto, Spain
Bisbee, Arizona, USA

Field-hunting tip

Look in fumaroles and oxidized copper deposits country — that is the host setting where chalcocyanite typically forms. If you start seeing chalcanthite, copper, tenorite in float, you are in the right ground. Field specimens usually show a crusts, fibrous aggregates, massive habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify chalcocyanite?+

Mohs hardness is 2.5. It typically shows a vitreous luster. The streak is white. Common colors include blue, pale blue.

Where is chalcocyanite found?+

Notable localities include Vesuvius, Italy; Chuquicamata, Chile; Rio Tinto, Spain; Bisbee, Arizona, USA.

How much is chalcocyanite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is chalcocyanite safe to handle?+

It contains toxic constituents. Contains copper which is toxic if ingested or inhaled; wash hands thoroughly after handling and avoid creating dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like chalcocyanite?+

Chalcocyanite is most often confused with Chalcanthite, Brochantite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with chalcocyanite?+

Chalcocyanite commonly co-occurs with Chalcanthite, Copper, Tenorite, Anglesite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does chalcocyanite form in?+

Chalcocyanite typically forms in fumaroles and oxidized copper deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is chalcocyanite used for?+

Chalcocyanite is used in collector.

Find chalcocyanite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.