Claudetite is a rare monoclinic form of arsenic trioxide that often forms as thin, delicate, platy crystals in the oxidized zones of arsenic-rich ore bodies. Due to its toxicity and delicate nature, it is strictly a mineral for advanced collectors and should be stored in a sealed container.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Claudetite

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

Is this claudetite?

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 claudetite with a known reference. Claudetite 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. Claudetite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Claudetite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, colorless.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: platy or thin tabular crystals, crusts, fan-like aggregates.

Often confused with

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

mineral

Arsenolite

Mohs 1.5

How to tell apart: Claudetite is noticeably harder (Mohs 2.5 vs. 1.5).

Often found alongside claudetite

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

All properties

Chemical formula: As₂O₃
Mohs hardness: 2.5
Density: 4.0 g/cm³
Colors: White Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Platy or Thin Tabular Crystals, Crusts, Fan-like Aggregates
Cleavage: Perfect in One Direction
Rarity: Rare
Uses: Collector
Host rock: Oxidized Zones of Arsenic-rich Hydrothermal Deposits
Typical price: $20-150 for thumbnail to small cabinet specimens

Where rockhounds find claudetite

Classic worldwide localities

Jáchymov, Czech Republic
Banská Štiavnica, Slovakia
Cerro de Pasco, Peru
Eureka, Utah, USA

Field-hunting tip

Look in oxidized zones of arsenic-rich hydrothermal deposits country — that is the host setting where claudetite typically forms. If you start seeing arsenopyrite, realgar, orpiment in float, you are in the right ground. Field specimens usually show a platy or thin tabular crystals, crusts, fan-like aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify claudetite?+

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

Where is claudetite found?+

Notable localities include Jáchymov, Czech Republic; Banská Štiavnica, Slovakia; Cerro de Pasco, Peru; Eureka, Utah, USA.

How much is claudetite worth?+

Typical asking prices fall in the range of $20-150 for thumbnail to small cabinet specimens. Quality, size, and provenance can move individual specimens well outside that range.

Is claudetite safe to handle?+

It contains toxic constituents. Contains arsenic, which is highly toxic if ingested or inhaled. Handle with extreme care, wear gloves, and wash hands thoroughly after touching specimens. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like claudetite?+

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

What minerals are found with claudetite?+

Claudetite commonly co-occurs with Arsenopyrite, Realgar, Orpiment, Arsenolite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does claudetite form in?+

Claudetite typically forms in oxidized zones of arsenic-rich hydrothermal deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is claudetite used for?+

Claudetite is used in collector.

Find claudetite on the map

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