Clinoatacamite is a monoclinic polymorph of the copper oxychloride Cu₂(OH)₃Cl. It is typically found in the oxidized zones of copper deposits, often appearing as distinct green, tabular crystals or crusts that are visually indistinguishable from other members of the atacamite group without laboratory analysis.
Is this clinoatacamite?
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 clinoatacamite with a known reference. Clinoatacamite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: greenish white.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine to vitreous.
- 4Match the color rangeCompare against the expected color range: green, dark greenish black, greenish blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: crystalline.
Often confused with
Clinoatacamite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Clinoatacamite leaves greenish white, Atacamite leaves apple-green.
How to tell apart: Streak differs, so Clinoatacamite leaves greenish white, Paratacamite leaves green; luster reads adamantine to vitreous on Clinoatacamite and vitreous on Paratacamite.
How to tell apart: Streak differs, so Clinoatacamite leaves greenish white, Botallackite leaves light green; luster reads adamantine to vitreous on Clinoatacamite and vitreous on Botallackite.
Often found alongside clinoatacamite
Minerals reported to co-occur with clinoatacamite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₂(OH)₃Cl
- Mohs hardness
- 3
- Density
- 3.71 g/cm³
- Colors
- Streak
- Greenish white
- Luster
- Adamantine to vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Crystalline
- Cleavage
- Perfect on {012}
- Rarity
- Uncommon
- Uses
- Collector, Scientific research
- Host rock
- An oxidation product of other copper minerals
Where rockhounds find clinoatacamite
Classic worldwide localities
- Calumet, Keweenaw Co., Michigan, and Mason Pass, near Yerington, Lyon Co., Nevada, USA
- Chuquicamata, and in the Sierra Gorda district, southwest of Calama, Antofagasta, Chile
- Remolinos, Atacama, Chile
- Wallaces Gully, Mount Painter, and Wallaroo, South Australia
- Castletown mine, Lochgilphead, Scotland
Field-hunting tip
Where it forms: An oxidation product of other copper minerals. If you start seeing atacamite, paratacamite, gypsum in float, you are in the right ground. Typical habit: crystalline. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify clinoatacamite?+
Where is clinoatacamite found?+
Is clinoatacamite safe to handle?+
What rocks look like clinoatacamite?+
What minerals are found with clinoatacamite?+
What kind of rock does clinoatacamite form in?+
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Find clinoatacamite on the map
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