Cyanochroite is a rare copper-bearing sulfate mineral primarily found in volcanic fumarole environments. It typically forms delicate blue to bluish-green tabular crystals or efflorescences that are highly susceptible to dehydration, requiring careful storage in a dry environment.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Cyanochroite

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

Is this cyanochroite?

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 cyanochroite with a known reference. Cyanochroite 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. Cyanochroite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Cyanochroite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: blue, bluish-green, colorless.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals, crusts, efflorescences.

Often confused with

Cyanochroite vs. its common look-alikes — and how to tell them apart in the field.

How to tell apart: Luster reads vitreous on Cyanochroite and silky on Pickeringite.

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Often found alongside cyanochroite

Minerals reported to co-occur with cyanochroite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: K₂Cu(SO₄)₂·6H₂O
Mohs hardness: 2.5
Density: 2.3 g/cm³
Colors: Blue Bluish-green Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Tabular Crystals, Crusts, Efflorescences
Cleavage: Poor On {001}
Rarity: Rare
Uses: Collector
Host rock: Fumaroles
Typical price: $20-150 thumbnail

Where rockhounds find cyanochroite

Classic worldwide localities

Vesuvius, Italy
Tolbachik volcano, Russia

Field-hunting tip

Look in fumaroles country — that is the host setting where cyanochroite typically forms. If you start seeing thenardite, gypsum, epsomite in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts, efflorescences habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify cyanochroite?+

Mohs hardness is 2.5. It typically shows a vitreous luster. The streak is white. Common colors include blue, bluish-green, colorless.

Where is cyanochroite found?+

Notable localities include Vesuvius, Italy; Tolbachik volcano, Russia.

How much is cyanochroite worth?+

Typical asking prices fall in the range of $20-150 thumbnail. Quality, size, and provenance can move individual specimens well outside that range.

Is cyanochroite safe to handle?+

It contains toxic constituents. Contains copper; wash hands thoroughly after handling to avoid ingestion or skin irritation. Store in a sealed container to prevent dehydration and dust inhalation. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like cyanochroite?+

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

What minerals are found with cyanochroite?+

Cyanochroite commonly co-occurs with Thenardite, Gypsum, Epsomite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does cyanochroite form in?+

Cyanochroite typically forms in fumaroles. Working float back to the host body is the standard way to chase a fresh occurrence.

What is cyanochroite used for?+

Cyanochroite is used in collector.

Find cyanochroite on the map

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