Clinoclase is a rare and striking copper arsenate mineral highly prized by collectors for its deep, rich blue-green color. It typically forms as radiating spray-like clusters or thin tabular crystals within the oxidized zones of copper deposits.
Is this clinoclase?
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 clinoclase with a known reference. Clinoclase sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: bluish green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous, pearly on cleavages.
- 4Match the color rangeCompare against the expected color range: dark verdigris green, blackish blue green, blackish green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, radiating aggregates, crusts, or drusy coatings.
Often confused with
Clinoclase vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Clinoclase leaves bluish green, Liroconite leaves pale blue to pale green.
How to tell apart: Streak differs, so Clinoclase leaves bluish green, Olivenite leaves olive-green to brown; luster reads vitreous, pearly on cleavages on Clinoclase and adamantine to vitreous, pearly to silky if fibrous on Olivenite.
How to tell apart: Streak differs, so Clinoclase leaves bluish green, Vivianite leaves white, altering to dark blue, brown.
Often found alongside clinoclase
Minerals reported to co-occur with clinoclase. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₃AsO₄(OH)₃
- Mohs hardness
- 2.5-3
- Density
- 4.38 g/cm³
- Colors
- Streak
- Bluish green
- Luster
- Vitreous, pearly on cleavages
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals, radiating aggregates, crusts, or drusy coatings
- Cleavage
- On {001}, perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral in the oxidized zone of some arsenic-rich hydrothermal base-metal deposits
Where rockhounds find clinoclase
Classic worldwide localities
- Mammoth and other mines, Tintic district, Juab Co., and the Gold Hill mine, Tooele Co., Utah, USA
- Majuba Hill mine, Antelope district, Pershing Co., Nevada, USA
- Cornwall, at Wheals Gorland and Unity, the Ting Tang and St. Day United mines, and others, Gwennap, in the Providence mine, Lelant, at Wheal Hazard, St. Just, England
- Bedford United mines, near Tavistock, Devon, England
- Sainte-Marie-aux-Mines, Haut-Rhin, and the Cap Garonne mine, near le Pradet, Var, France
- Altväter samt Eschig mine, near Sayda, Saxony, Germany
Field-hunting tip
Where it forms: A rare secondary mineral in the oxidized zone of some arsenic-rich hydrothermal base-metal deposits. If you start seeing olivenite, cornwallite, cornubite in float, you are in the right ground. Typical habit: tabular crystals, radiating aggregates, crusts, or drusy coatings. Train your eye for that shape before scanning the outcrop.
Common questions
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Find clinoclase on the map
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