Capgaronnite is an extremely rare mercury-silver halide mineral named after its type locality at the Cap Garonne mine in France. It typically forms small, clear, tabular crystals in supergene environments where lead and copper-rich ores have undergone alteration.
Is this capgaronnite?
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 capgaronnite with a known reference. Capgaronnite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Capgaronnite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Capgaronnite typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, pale yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular crystals.
Often confused with
Capgaronnite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads adamantine on Capgaronnite and vitreous on Halite.
How to tell apart: Luster reads adamantine on Capgaronnite and resinous on Chlorargyrite.
How to tell apart: Streak differs — Capgaronnite leaves white, Boleite leaves light blue; luster reads adamantine on Capgaronnite and vitreous on Boleite.
Often found alongside capgaronnite
Minerals reported to co-occur with capgaronnite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- HgAgClBrI
- Mohs hardness
- 2.5
- Density
- 7.39 g/cm³
- Streak
- White
- Luster
- Adamantine
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular Crystals
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Sedimentary Copper Deposits
- Typical price
- $100-500+ depending on crystal size and quality
Where rockhounds find capgaronnite
Classic worldwide localities
- Cap Garonne mine, Var, France
Field-hunting tip
Look in sedimentary copper deposits country — that is the host setting where capgaronnite typically forms. If you start seeing quartz, galena, barite in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify capgaronnite?+
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Find capgaronnite on the map
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