Cyanotrichite is a secondary copper mineral easily identified by its vibrant sky-blue color and delicate, velvety acicular habit. It typically forms as radiating tufts or crusts in the oxidized zones of copper-rich hydrothermal ore bodies.
Is this cyanotrichite?
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 cyanotrichite with a known reference. Cyanotrichite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Cyanotrichite leaves a pale blue streak.
- 3Read the lusterHold the specimen under a strong light. Cyanotrichite typically shows a silky luster.
- 4Match the color rangeCompare against the expected color range: sky-blue, azure-blue.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular crystals, radiating tufts, velvety crusts.
Often confused with
Cyanotrichite 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); streak differs — Cyanotrichite leaves pale blue, Azurite leaves light blue; luster reads silky on Cyanotrichite and vitreous to dull on Azurite.
How to tell apart: Luster reads silky on Cyanotrichite and pearly on Aurichalcite.
How to tell apart: Luster reads silky on Cyanotrichite and vitreous on Linarite.
Often found alongside cyanotrichite
Minerals reported to co-occur with cyanotrichite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₄Al₂(SO₄)(OH)₁₂·2H₂O
- Mohs hardness
- 2
- Density
- 2.7-2.9 g/cm³
- Colors
- Streak
- Pale Blue
- Luster
- Silky
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular Crystals, Radiating Tufts, Velvety Crusts
- Cleavage
- Perfect in One Direction
- Rarity
- Uncommon
- Uses
- Collector, Specimen
- Host rock
- Oxidized Copper Deposits
- Typical price
- $15-150 per specimen depending on crystal size and matrix
Where rockhounds find cyanotrichite
Classic worldwide localities
- Chessy-les-Mines, France
- Laurion, Greece
- Bisbee, Arizona, USA
- Tintic District, Utah, USA
- Tsumeb, Namibia
Field-hunting tip
Look in oxidized copper deposits country — that is the host setting where cyanotrichite typically forms. If you start seeing brochantite, malachite, azurite in float, you are in the right ground. Field specimens usually show a acicular crystals, radiating tufts, velvety crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find cyanotrichite on the map
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