Gabrielite is an extremely rare sulfosalt mineral found almost exclusively in the Binn Valley of Switzerland. It typically forms small, gray to black, tabular crystals embedded in dolomitic marble or associated with other rare arsenic-bearing sulfosalts.
Is this gabrielite?
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 gabrielite with a known reference. Gabrielite sits at Mohs 1.5-2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: blackish red.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: triclinic. Typical habit: prismatic, pseudo hexagonal, striated.
Often confused with
Gabrielite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Gabrielite leaves blackish red, Smithite leaves vermilion; luster reads metallic on Gabrielite and adamantine on Smithite.
How to tell apart: Streak differs, so Gabrielite leaves blackish red, Hutchinsonite leaves red; luster reads metallic on Gabrielite and adamantine to submetallic on Hutchinsonite.
Often found alongside gabrielite
Minerals reported to co-occur with gabrielite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Tl₂AgCu₂As₃S₇
- Mohs hardness
- 1.5-2
- Density
- 5.41 g/cm³
- Colors
- Streak
- Blackish red
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Triclinic
- Crystal habit
- Prismatic, pseudo hexagonal, striated
- Cleavage
- Perfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A late-stage mineral in vugs in a hydrothermally-altered dolomitic marble
Where rockhounds find gabrielite
Classic worldwide localities
- Lengenbach, Binntal, Canton Valais, Switzerland
Field-hunting tip
Where it forms: A late-stage mineral in vugs in a hydrothermally-altered dolomitic marble. If you start seeing hutchinsonite, hatchite, edenharterite in float, you are in the right ground. Typical habit: prismatic, pseudo hexagonal, striated. Train your eye for that shape before scanning the outcrop.
Common questions
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Find gabrielite on the map
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