Herbertsmithite is a rare copper zinc hydroxychloride that forms distinctive bright green rhombohedral crystals. It is highly sought after by collectors for its significance in quantum physics research as a candidate for a quantum spin liquid. It is typically found as a secondary mineral in oxidized zones of copper deposits.

Hardness

3-3.5

Mohs

Luster

Vitreous

Transparency

Transparent

mineralrare

Herbertsmithite

Hardness: 3-3.5
Luster: Vitreous
Transparency: Transparent

Is this herbertsmithite?

4-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 herbertsmithite with a known reference. Herbertsmithite sits at Mohs 3-3.5, softer than the next harder reference, harder than the previous one.
2
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
3
Match the color range
Compare against the expected color range: dark green, blue green.
4
Look at form & habit
Crystal system: trigonal. Typical habit: aggregates, rhombohedral crystals.

Often confused with

Herbertsmithite vs. its common look-alikes, and how to tell them apart in the field.

How to tell apart: Luster reads vitreous on Herbertsmithite and adamantine to vitreous on Atacamite.

How to tell apart: Luster reads vitreous on Herbertsmithite and adamantine to vitreous on Clinoatacamite.

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Often found alongside herbertsmithite

Minerals reported to co-occur with herbertsmithite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Cu₃Zn(OH)₆Cl₂
Mohs hardness: 3-3.5
Density: 3.75-3.95 g/cm³
Colors: Dark green Blue green
Luster: Vitreous
Transparency: Transparent
Crystal system: Trigonal
Crystal habit: Aggregates, rhombohedral crystals
Cleavage: Good {101̄1}
Rarity: Rare
Uses: Collector
Host rock: A secondary mineral in the oxidation zone of polymetallic mineral deposits

Where rockhounds find herbertsmithite

Classic worldwide localities

Mina Los Tres Presidentes, Sierra Gorda, Chile, Iran
Kali Kafi and Chah Khouni mines, Anarak, Iran

Field-hunting tip

Where it forms: A secondary mineral in the oxidation zone of polymetallic mineral deposits. If you start seeing gypsum, opal, dioptase in float, you are in the right ground. Typical habit: aggregates, rhombohedral crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify herbertsmithite?+

Mohs hardness is 3-3.5. Luster: vitreous. Common colors include dark green, blue green.

Where is herbertsmithite found?+

Notable localities include Mina Los Tres Presidentes, Sierra Gorda, Chile, Iran; Kali Kafi and Chah Khouni mines, Anarak, Iran.

Is herbertsmithite safe to handle?+

Herbertsmithite contains copper. Contains copper and chlorine; wash hands thoroughly after handling specimens to avoid ingestion of powder or dust.

What rocks look like herbertsmithite?+

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

What minerals are found with herbertsmithite?+

Herbertsmithite commonly co-occurs with Gypsum, Opal, Dioptase, Wulfenite, Hemimorphite, Chrysocolla. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does herbertsmithite form in?+

Where it forms: A secondary mineral in the oxidation zone of polymetallic mineral deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is herbertsmithite used for?+

Herbertsmithite is used in collector.

Find herbertsmithite on the map

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