Atacamite is a striking copper chloride mineral known for its vivid, intense green color. It typically forms as a secondary mineral in the oxidized zones of copper deposits, often found as radiating sprays of acicular crystals or crusts within arid, desert environments.
Is this atacamite?
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 atacamite with a known reference. Atacamite sits at Mohs 3-3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Atacamite leaves a apple green streak.
- 3Read the lusterHold the specimen under a strong light. Atacamite typically shows a adamantine to vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark green, bright green, emerald green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic, acicular, fibrous, or granular aggregates.
Often confused with
Atacamite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Atacamite leaves apple green, Malachite leaves light green; luster reads adamantine to vitreous on Atacamite and vitreous on Malachite.
How to tell apart: Streak differs — Atacamite leaves apple green, Brochantite leaves pale-green; luster reads adamantine to vitreous on Atacamite and vitreous on Brochantite.
How to tell apart: Streak differs — Atacamite leaves apple green, Libethenite leaves pale green; luster reads adamantine to vitreous on Atacamite and vitreous on Libethenite.
Often found alongside atacamite
Minerals reported to co-occur with atacamite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₂Cl(OH)₃
- Mohs hardness
- 3-3.5
- Density
- 3.7-3.8 g/cm³
- Streak
- Apple Green
- Luster
- Adamantine to Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic, Acicular, Fibrous, Or Granular Aggregates
- Cleavage
- Perfect in One Direction
- Rarity
- Uncommon
- Uses
- Collector, Scientific Research
- Host rock
- Oxidized Zones of Copper Deposits in Arid Environments
- Typical price
- $10-100 per specimen depending on crystal quality and size
Where rockhounds find atacamite
1 mapped spotsClassic worldwide localities
- Atacama Desert, Chile
- Burra, South Australia
- Chuquicamata, Chile
- Wallaroo, Australia
- Milpillas Mine, Mexico
Field-hunting tip
Look in oxidized zones of copper deposits in arid environments country — that is the host setting where atacamite typically forms. If you start seeing malachite, chrysocolla, brochantite in float, you are in the right ground. Field specimens usually show a prismatic, acicular, fibrous, or granular aggregates habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Mexico — start trip planning there.
Common questions
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Find atacamite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
