Botallackite is a rare copper halide mineral typically forming as thin, platy crystals in oxidized copper deposits. It is best identified by its bright green color and association with other secondary copper minerals in historic mining districts like Cornwall.
Is this botallackite?
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 botallackite with a known reference. Botallackite 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: light green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: blue green, green, light blue green, light green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, crusts, radial aggregates.
Often confused with
Botallackite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Botallackite leaves light green, Atacamite leaves apple-green; luster reads vitreous on Botallackite and adamantine to vitreous on Atacamite.
How to tell apart: Streak differs, so Botallackite leaves light green, Paratacamite leaves green.
How to tell apart: Streak differs, so Botallackite leaves light green, Malachite leaves pale green; luster reads vitreous on Botallackite and adamantine to vitreous; silky if fibrous; dull to earthy if massive on Malachite.
Often found alongside botallackite
Minerals reported to co-occur with botallackite. 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
- Density
- 3.6 g/cm³
- Colors
- Streak
- Light green
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy crystals, crusts, radial aggregates
- Cleavage
- One direction, good, ⊥ Z
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In copper-bearing deposits, in areas with high chlorine concentrations or weathered while exposed to seawater; a reaction product of slag immersed in seawater
Where rockhounds find botallackite
Classic worldwide localities
- Bisbee, Cochise Co., Arizona, USA
- Wheal Cock and West Wheal Owles, the Botallack and Levant mines, St. Just, and a few other places in Cornwall, England
- Southwick Cliffs, near Dalbeattie, Kirkcudbrightshire, Scotland
- Castletown mine, Lochgilphead, Scotland
- Found in the Dooneen mine, Allihies, Co. Cork, Ireland
- Juliushütte, Astfeld, Harz Mountains, Germany, in slag
Field-hunting tip
Where it forms: In copper-bearing deposits, in areas with high chlorine concentrations or weathered while exposed to seawater; a reaction product of slag immersed in seawater. If you start seeing atacamite, paratacamite, gypsum in float, you are in the right ground. Typical habit: platy crystals, crusts, radial aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
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Find botallackite on the map
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