Bernardite is a rare thallium-arsenic sulfosalt primarily found at the Allchar deposit in North Macedonia. It typically occurs as small, flattened, deep-red to black tabular crystals that are highly sought after by systematic mineral collectors.
Is this bernardite?
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 bernardite with a known reference. Bernardite sits at Mohs ~2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: red.
- 3Read the lusterHold the specimen under a strong light. Luster: dull.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals.
Often confused with
Bernardite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Bernardite leaves red, Realgar leaves red-orange to red; luster reads dull on Bernardite and resinous to greasy on Realgar.
How to tell apart: Streak differs, so Bernardite leaves red, Smithite leaves vermilion; luster reads dull on Bernardite and adamantine on Smithite.
Often found alongside bernardite
Minerals reported to co-occur with bernardite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- TlAs₅S₈
- Mohs hardness
- ~2
- Density
- 4.5 g/cm³
- Colors
- Streak
- Red
- Luster
- Dull
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a hydrothermal deposit with other As–Tl sulfide minerals
Where rockhounds find bernardite
Classic worldwide localities
- Alšar (Allchar), near Rošden, Macedonia (type locality)
- Lengenbach quarry, Binntal, Valais, Switzerland
Field-hunting tip
Where it forms: In a hydrothermal deposit with other As–Tl sulfide minerals. If you start seeing realgar, orpiment, hutchinsonite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find bernardite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
