Conichalcite is a vibrant green secondary mineral often found as attractive botryoidal or crust-like coatings on rock surfaces. It forms in the oxidized zones of copper-arsenic deposits and is frequently collected for its bright coloration and pleasing globular habits.
Is this conichalcite?
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 conichalcite with a known reference. Conichalcite sits at Mohs 4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to somewhat greasy.
- 4Match the color rangeCompare against the expected color range: yellow green, emerald green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: fibrous, massive, reniform.
Often confused with
Conichalcite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Conichalcite leaves green, Austinite leaves white; luster reads vitreous to somewhat greasy on Conichalcite and subadamantine to silky in aggregates on Austinite.
How to tell apart: Conichalcite is noticeably harder (Mohs 4.5 vs. 3); streak differs, so Conichalcite leaves green, Olivenite leaves olive-green to brown; luster reads vitreous to somewhat greasy on Conichalcite and adamantine to vitreous, pearly to silky if fibrous on Olivenite.
How to tell apart: Streak differs, so Conichalcite leaves green, Malachite leaves pale green; luster reads vitreous to somewhat greasy on Conichalcite and adamantine to vitreous; silky if fibrous; dull to earthy if massive on Malachite.
Often found alongside conichalcite
Minerals reported to co-occur with conichalcite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaCu(AsO₄)(OH)
- Mohs hardness
- 4.5
- Density
- 4.33 g/cm³
- Streak
- Green
- Luster
- Vitreous to somewhat greasy
- Transparency
- Subtranslucent
- Crystal system
- Orthorhombic
- Crystal habit
- Fibrous, massive, reniform
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector, Mineral specimen
- Host rock
- An uncommon secondary mineral in the oxidized zone of copper deposits, typically an alteration product of enargite
Where rockhounds find conichalcite
Classic worldwide localities
- American Eagle and a number of other mines in the Tintic district, Juab Co., and in the Gold Hill mine, Tooele Co., Utah, USA
- Bisbee, Cochise Co., Arizona, USA
- Bristol mine, Lincoln Co., and the Empire-Nevada mine, Yerington, Lyon Co., USA
- Hinojosa de Córdoba, Andalusia, Spain
- Wheal Kendall, St. Hilary, and the Hingston Down quarry, Calstock, Cornwall, England
- Caldbeck Fells, Cumbria, England
Field-hunting tip
Where it forms: An uncommon secondary mineral in the oxidized zone of copper deposits, typically an alteration product of enargite. If you start seeing austinite, olivenite, clinoclase in float, you are in the right ground. Typical habit: fibrous, massive, reniform. Train your eye for that shape before scanning the outcrop.
Common questions
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Find conichalcite on the map
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