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, 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.