Lapeyreite is a very rare copper arsenate mineral known primarily from its type locality in Utah. It typically occurs as small, delicate, dark pistachio-green bladed crystals often associated with other rare copper secondary minerals in oxidized hydrothermal zones.

Hardness

Mohs

Luster

Vitreous to adamantine

Streak

Yellowish green

Transparency

Transparent

mineralrare

Lapeyreite

Hardness: 3
Luster: Vitreous to adamantine
Streak: Yellowish green
Transparency: Transparent

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Is this lapeyreite?

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 lapeyreite with a known reference. Lapeyreite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: yellowish green.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous to adamantine.
4
Match the color range
Compare against the expected color range: dark pistachio-green.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: bladed crystals, aggregates.

Often confused with

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

mineral

Clinoclase

Mohs 2.5-3

How to tell apart: Streak differs, so Lapeyreite leaves yellowish green, Clinoclase leaves bluish green.

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Often found alongside lapeyreite

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

All properties

Chemical formula: Cu₃O[AsO₃(OH)]₂·H₂O
Mohs hardness: 3
Density: 4.385 g/cm³
Colors: Dark pistachio-green
Streak: Yellowish green
Luster: Vitreous to adamantine
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Bladed crystals, aggregates
Cleavage: Perfect on {001}
Rarity: Rare
Uses: Collector
Host rock: A secondary mineral in geodes of cuprite in a weathering zone

Where rockhounds find lapeyreite

Classic worldwide localities

Roua, Dôme de Barrot, Departement Alpes-Maritimes, France (type locality)

Field-hunting tip

Where it forms: A secondary mineral in geodes of cuprite in a weathering zone. If you start seeing trippkeite, olivenite, malachite in float, you are in the right ground. Typical habit: bladed crystals, aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify lapeyreite?+

Mohs hardness is 3. Luster: vitreous to adamantine. The streak is yellowish green. Common colors include dark pistachio-green.

Where is lapeyreite found?+

Notable localities include Roua, Dôme de Barrot, Departement Alpes-Maritimes, France (type locality).

Is lapeyreite safe to handle?+

Lapeyreite contains arsenic and copper and calls for real care. Contains arsenic and copper; avoid ingestion, inhalation of dust, or skin contact. Wash hands thoroughly after handling.

What rocks look like lapeyreite?+

Lapeyreite is most often confused with Clinoclase. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with lapeyreite?+

Lapeyreite commonly co-occurs with Trippkeite, Olivenite, Malachite, Gilmarite, Cornubite, Connellite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does lapeyreite form in?+

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

What is lapeyreite used for?+

Lapeyreite is used in collector.

Find lapeyreite on the map

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