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.
Is this claudetite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch claudetite with a known reference. Claudetite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous; pearly on cleavage surfaces.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy.
Often confused with
Claudetite vs. its common look-alikes, and how to tell them apart in the field.
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
- 4.14-4.15 g/cm³
- Streak
- White
- Luster
- Vitreous; pearly on cleavage surfaces
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Platy
- Cleavage
- Perfect micaceous cleavage on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary oxidation product derived from realgar, arsenopyrite, or other arsenic-bearing minerals
Where rockhounds find claudetite
Classic worldwide localities
- United Verde mine, Jerome, Yavapai Co., Arizona, and in the Tintic Standard mine, near Dividend, East Tintic district, Utah Co., Utah, both from mine fires, USA
- A sulfur prospect about 10 km north of the 4 S Ranch, Imperial Co., California, USA
- San Domingo mines, Algarve, Portugal
- Calañas, Andalusia, Spain
- Large cleavages from Rio Tinto, Huelva, Spain
- Lasalle mine, Decazeville, Aveyron, France
Field-hunting tip
Where it forms: A secondary oxidation product derived from realgar, arsenopyrite, or other arsenic-bearing minerals. If you start seeing arsenolite, realgar, orpiment in float, you are in the right ground. Typical habit: platy. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify claudetite?+
Where is claudetite found?+
Is claudetite safe to handle?+
What rocks look like claudetite?+
What minerals are found with claudetite?+
What kind of rock does claudetite form in?+
What is claudetite used for?+
Find claudetite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
