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. Streak: pale blue.
- 3Read the lusterHold the specimen under a strong light. Luster: silky.
- 4Match the color rangeCompare against the expected color range: sky blue, light blue, dark blue.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular, druse, spherical.
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); luster reads silky on Cyanotrichite and vitreous to subadamantine on Azurite.
How to tell apart: Streak differs, so Cyanotrichite leaves pale blue, Aurichalcite leaves light blue.
How to tell apart: Luster reads silky on Cyanotrichite and vitreous to subadamantine 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
- 2.74-2.95 g/cm³
- Streak
- Pale blue
- Luster
- Silky
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular, druse, spherical
- Cleavage
- Good
- Rarity
- Uncommon
- Uses
- Collector, Specimen
- Host rock
- An uncommon secondary mineral in the oxidized portions of copper sulfide deposits
Where rockhounds find cyanotrichite
Classic worldwide localities
- Grandview (Last Chance) mine, Grand Canyon National Park, Coconino Co., Arizona, USA
- Maid of Sunshine mine, Courtland, and Bisbee, Cochise Co., Arizona, USA
- Morenci, Greenlee Co., Arizona, USA
- Jerome, Yavapai Co., Arizona, USA
- Moldova Nouǎ (Moldova), Romania
- Cap Garonne mine, near le Pradet, Var, France
Field-hunting tip
Where it forms: An uncommon secondary mineral in the oxidized portions of copper sulfide deposits. If you start seeing brochantite, spangolite, chalcophyllite in float, you are in the right ground. Typical habit: acicular, druse, spherical. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cyanotrichite?+
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Is cyanotrichite safe to handle?+
What rocks look like cyanotrichite?+
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Find cyanotrichite on the map
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