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.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Eriochalcite

Hardness: 2.5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this eriochalcite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch eriochalcite with a known reference. Eriochalcite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Eriochalcite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Eriochalcite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: blue, blue-green.
5
Look at form & habit
Crystal 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.

mineral

Atacamite

Mohs 3-3.5

How to tell apart: Streak differs — Eriochalcite leaves white, Atacamite leaves apple green; luster reads vitreous on Eriochalcite and adamantine to vitreous on Atacamite.

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: 2.38 g/cm³
Colors: Blue Blue-green
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Crusts, Efflorescences, Stalactitic
Cleavage: Distinct
Rarity: Rare
Uses: Collector
Host rock: Volcanic Fumaroles and Oxidized Copper Deposits
Typical price: $50-300 per specimen

Where rockhounds find eriochalcite

Classic worldwide localities

Vesuvius, Italy
Chuquicamata, Chile
Tsumeb, Namibia

Field-hunting tip

Look in volcanic fumaroles and oxidized copper deposits country — that is the host setting where eriochalcite typically forms. If you start seeing atacamite, tenorite, cuprite in float, you are in the right ground. Field specimens usually show a crusts, efflorescences, stalactitic habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify eriochalcite?+

Mohs hardness is 2.5. It typically shows a vitreous luster. The streak is white. Common colors include blue, blue-green.

Where is eriochalcite found?+

Notable localities include Vesuvius, Italy; Chuquicamata, Chile; Tsumeb, Namibia.

How much is eriochalcite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is eriochalcite safe to handle?+

It contains toxic constituents. Contains copper and chlorine; harmful if ingested or inhaled as dust. Handle with care and wash hands thoroughly after handling. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like eriochalcite?+

Eriochalcite is most often confused with Atacamite, Chalcanthite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with eriochalcite?+

Eriochalcite commonly co-occurs with Atacamite, Tenorite, Cuprite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does eriochalcite form in?+

Eriochalcite typically forms in volcanic fumaroles and oxidized copper deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is eriochalcite used for?+

Eriochalcite is used in collector.

Find eriochalcite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.