Gilmarite is a rare copper arsenate mineral typically found as small, bright green acicular crystals or delicate radiating sprays. It is primarily identified by its occurrence in highly oxidized copper-arsenic zones, most notably at the Cap Garonne mine in France.
Is this gilmarite?
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 gilmarite with a known reference. Gilmarite 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. Gilmarite leaves a light green streak.
- 3Read the lusterHold the specimen under a strong light. Gilmarite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: green, yellowish-green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular crystals, radial aggregates.
Often confused with
Gilmarite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside gilmarite
Minerals reported to co-occur with gilmarite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₃(AsO₄)(OH)₃
- Mohs hardness
- 3
- Density
- 3.5 g/cm³
- Colors
- Streak
- Light Green
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular Crystals, Radial Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Copper-arsenic Deposits
- Typical price
- $50-300 per specimen depending on size and quality
Where rockhounds find gilmarite
Classic worldwide localities
- Cap Garonne mine (France)
- Laurion (Greece)
Field-hunting tip
Look in oxidized copper-arsenic deposits country — that is the host setting where gilmarite typically forms. If you start seeing clinoclase, cornwallite, olivenite in float, you are in the right ground. Field specimens usually show a acicular crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify gilmarite?+
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How much is gilmarite worth?+
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Find gilmarite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
