Tolbachite is an extremely rare copper chloride mineral discovered in volcanic fumaroles. It is typically found as dark red, tabular crusts or small crystal coatings associated with other volcanic sublimates. Due to its solubility, it must be kept in a dry environment to prevent degradation.
Is this tolbachite?
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 tolbachite with a known reference. Tolbachite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Tolbachite leaves a yellowish red streak.
- 3Read the lusterHold the specimen under a strong light. Tolbachite typically shows a subadamantine luster.
- 4Match the color rangeCompare against the expected color range: dark red, copper red.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular crystals, crusts, or coatings.
Often confused with
Tolbachite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Tolbachite leaves yellowish red, Eriochalcite leaves white; luster reads subadamantine on Tolbachite and vitreous on Eriochalcite.
How to tell apart: Atacamite is the harder of the two (Mohs 3-3.5 vs. 2); streak differs — Tolbachite leaves yellowish red, Atacamite leaves apple green; luster reads subadamantine on Tolbachite and adamantine to vitreous on Atacamite.
Often found alongside tolbachite
Minerals reported to co-occur with tolbachite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuCl₂
- Mohs hardness
- 2
- Density
- 3.32 g/cm³
- Colors
- Streak
- Yellowish Red
- Luster
- Subadamantine
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular Crystals, Crusts, Or Coatings
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Fumarolic Deposits in Volcanic Environments
- Typical price
- $100-500 for high quality rare specimens
Where rockhounds find tolbachite
Classic worldwide localities
- Tolbachik volcano, Kamchatka, Russia
Field-hunting tip
Look in fumarolic deposits in volcanic environments country — that is the host setting where tolbachite typically forms. If you start seeing eriochalcite, chalcocyanite, tenorite in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts, or coatings habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find tolbachite on the map
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