Laforêtite is an extremely rare silver indium sulfide mineral typically found as microscopic grains within other sulfides. It is primarily identified through laboratory analysis of samples from its type locality at the La Fôret mine in France.
Is this laforêtite?
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 laforêtite with a known reference. Laforêtite sits at Mohs ~3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: chocolate brown.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: brown.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: inclusions, microscopic crystals.
Often confused with
Laforêtite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Laforêtite leaves chocolate brown, Chalcostibite leaves black.
How to tell apart: Laforêtite is noticeably harder (Mohs ~3 vs. 2); streak differs, so Laforêtite leaves chocolate brown, Emplectite leaves black.
Often found alongside laforêtite
Minerals reported to co-occur with laforêtite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AgInS₂
- Mohs hardness
- ~3
- Density
- 4.93 g/cm³
- Colors
- Streak
- Chocolate brown
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Tetragonal
- Crystal habit
- Inclusions, microscopic crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a dump sample from a vein-type hydrothermal ore deposit (Montgros mine, France); in a vein-type hydrothermal ore deposit (Toyoha mine, Japan)
Where rockhounds find laforêtite
Classic worldwide localities
- Montgros Pb–Zn mine, near La Boriette, about 10 km southwest of Langeac, Haute-Loire, France (type locality)
- Toyoha Pb–Zn–Ag mine, 40 km southwest of Sapporo, Hokkaido, Japan
Field-hunting tip
Where it forms: In a dump sample from a vein-type hydrothermal ore deposit (Montgros mine, France); in a vein-type hydrothermal ore deposit (Toyoha mine, Japan). If you start seeing galena, sphalerite, barite in float, you are in the right ground. Typical habit: inclusions, microscopic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify laforêtite?+
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Is laforêtite safe to handle?+
What rocks look like laforêtite?+
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Find laforêtite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
