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, so 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, so 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, so 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, 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.
