Lammerite is a rare copper arsenate mineral that occurs as small, intense green, transparent crystals in oxidized hydrothermal ore deposits. It is highly sought after by advanced collectors for its distinct color and scarcity, often found as radiating groups on a matrix of weathered sulfide ores.

Hardness

3-4

Mohs

Luster

Vitreous

Transparency

Transparent

mineralrare

Lammerite

Hardness: 3-4
Luster: Vitreous
Transparency: Transparent

Is this lammerite?

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 lammerite with a known reference. Lammerite sits at Mohs 3-4, 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.
4
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic crystals, radial aggregates.

Often confused with

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

How to tell apart: Luster reads vitreous on Lammerite and adamantine to vitreous, pearly to silky if fibrous on Olivenite.

Compare →

Often found alongside lammerite

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

All properties

Chemical formula: Cu₃(AsO₄)₂
Mohs hardness: 3-4
Density: 5.18 g/cm³
Colors: Dark green
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Prismatic crystals, radial aggregates
Cleavage: None observed
Rarity: Rare
Uses: Collector
Host rock: The product of post-eruption fumarolic reactions (400–650 °C) in an active volcano

Where rockhounds find lammerite

Classic worldwide localities

Second Scoria cone of the Northern Branch of the Great fissure Tolbachik eruption (1975–1976), Kamchatka peninsula, Russia

Field-hunting tip

Where it forms: The product of post-eruption fumarolic reactions (400–650 °C) in an active volcano. If you start seeing euchlorine, piypite, alumokluchevskite in float, you are in the right ground. Typical habit: prismatic crystals, radial aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify lammerite?+

Mohs hardness is 3-4. Luster: vitreous. Common colors include dark green.

Where is lammerite found?+

Notable localities include Second Scoria cone of the Northern Branch of the Great fissure Tolbachik eruption (1975–1976), Kamchatka peninsula, Russia.

Is lammerite safe to handle?+

Lammerite contains arsenic and copper and calls for real care. Contains arsenic and copper; wash hands thoroughly after handling and avoid inhaling dust or powder.

What rocks look like lammerite?+

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

What minerals are found with lammerite?+

Lammerite commonly co-occurs with Euchlorine, Piypite, Alumokluchevskite, Alarsite, Lammerite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does lammerite form in?+

Where it forms: The product of post-eruption fumarolic reactions (400–650 °C) in an active volcano. Working float back to the host body is the standard way to chase a fresh occurrence.

What is lammerite used for?+

Lammerite is used in collector.

Find lammerite on the map

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