Pierrotite is a very rare thallium-arsenic sulfosalt primarily known from the unique Allchar deposit in North Macedonia. It typically appears as lead-gray acicular crystals that can be difficult to distinguish from other sulfosalts without advanced analytical techniques.
Is this pierrotite?
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 pierrotite with a known reference. Pierrotite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: reddish black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic, lively.
- 4Match the color rangeCompare against the expected color range: grayish black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: aggregates, granular.
Often confused with
Pierrotite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Pierrotite is noticeably harder (Mohs 3.5 vs. 2); streak differs, so Pierrotite leaves reddish black, Stibnite leaves lead-gray.
How to tell apart: Pierrotite is noticeably harder (Mohs 3.5 vs. 1.5-2); streak differs, so Pierrotite leaves reddish black, Realgar leaves red-orange to red; luster reads metallic, lively on Pierrotite and resinous to greasy on Realgar.
How to tell apart: Pierrotite is noticeably harder (Mohs 3.5 vs. 2-2.5); streak differs, so Pierrotite leaves reddish black, Lorándite leaves cherry-red.
Often found alongside pierrotite
Minerals reported to co-occur with pierrotite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Tl₂Sb₁₀As₄S₁₈
- Mohs hardness
- 3.5
- Density
- 4.97 g/cm³
- Colors
- Streak
- Reddish black
- Luster
- Metallic, lively
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Aggregates, granular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In quartz veins (Jas Roux, France)
Where rockhounds find pierrotite
Classic worldwide localities
- Lookout Pass, Tooele Co., Utah, USA
- Jas Roux deposit, 10 km east of Chapelle-en-Valgaudemar, Hautes-Alpes, France (type locality)
- Alšar (Allchar), near Rošden, Macedonia
Field-hunting tip
Where it forms: In quartz veins (Jas Roux, France). If you start seeing stibnite, realgar, pyrite in float, you are in the right ground. Typical habit: aggregates, granular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify pierrotite?+
Where is pierrotite found?+
Is pierrotite safe to handle?+
What rocks look like pierrotite?+
What minerals are found with pierrotite?+
What kind of rock does pierrotite form in?+
What is pierrotite used for?+
Find pierrotite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
