Eriochalcite is a rare, water-soluble copper chloride mineral often found as crusts or efflorescences in volcanic environments. It is highly sensitive to humidity and must be stored in a dry, sealed container to prevent it from deliquescing or altering.
Is this eriochalcite?
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 eriochalcite with a known reference. Eriochalcite 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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: blue green, green blue.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: crusts, efflorescences, stalactitic.
Often confused with
Eriochalcite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside eriochalcite
Minerals reported to co-occur with eriochalcite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuCl₂·2H₂O
- Mohs hardness
- 2.5
- Density
- 2.4 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Crusts, efflorescences, stalactitic
- Cleavage
- Perfect on {110}; good on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As an encrustation around fumaroles (Vesuvius, Italy); a product of weathering in a copper sulfide deposit in an arid climate (Quetena, Chile)
Where rockhounds find eriochalcite
Classic worldwide localities
- Hawthorne, Mineral Co., Nevada, USA
- Vesuvius, Campania, Italy
- Tolbachik fissure volcano, Kamchatka Peninsula, Russia
- Quetena, west of Calama, Antofagasta, Chile
- Mt. Gunson copper mine, Stuart Shelf, and Moonta, South Australia
Field-hunting tip
Where it forms: As an encrustation around fumaroles (Vesuvius, Italy); a product of weathering in a copper sulfide deposit in an arid climate (Quetena, Chile). If you start seeing melanothallite, euchlorine, chalcocyanite in float, you are in the right ground. Typical habit: crusts, efflorescences, stalactitic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify eriochalcite?+
Where is eriochalcite found?+
Is eriochalcite safe to handle?+
What rocks look like eriochalcite?+
What minerals are found with eriochalcite?+
What kind of rock does eriochalcite form in?+
What is eriochalcite used for?+
Find eriochalcite on the map
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