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, so 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, 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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