Laffittite is an extremely rare silver mercury arsenic sulfosalt mineral found almost exclusively in the Jas Roux deposit in France. It typically forms small, dark red tabular crystals and is highly sought after by advanced mineral collectors specializing in rare sulfosalts.
Is this laffittite?
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 laffittite with a known reference. Laffittite 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: pale cherry-red to brownish red.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic, adamantine.
- 4Match the color rangeCompare against the expected color range: dark red.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals.
Often confused with
Laffittite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Laffittite is noticeably harder (Mohs 3.5 vs. 2-2.5); streak differs, so Laffittite leaves pale cherry-red to brownish red, Proustite leaves vermilion; luster reads metallic, adamantine on Laffittite and adamantine on Proustite.
How to tell apart: Laffittite is noticeably harder (Mohs 3.5 vs. 1.5-2); streak differs, so Laffittite leaves pale cherry-red to brownish red, Smithite leaves vermilion; luster reads metallic, adamantine on Laffittite and adamantine on Smithite.
Often found alongside laffittite
Minerals reported to co-occur with laffittite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AgHgAsS₃
- Mohs hardness
- 3.5
- Density
- 6.11 g/cm³
- Colors
- Streak
- Pale cherry-red to brownish red
- Luster
- Metallic, adamantine
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals
- Cleavage
- Good to imperfect on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- With other arsenic sulfides, in hydrothermal deposits
Where rockhounds find laffittite
Classic worldwide localities
- Getchell mine, Potosi district, Humboldt Co., Nevada, USA
- Jas Roux deposit, 10 km east of Chapelle-en-Valgaudemar, Hautes-Alpes, France (type locality)
- Chauvai Sb–Hg deposit, Fergana Valley, Alai Range, southern Kyrgyzstan
Field-hunting tip
Where it forms: With other arsenic sulfides, in hydrothermal deposits. If you start seeing smithite, stibnite, pierrotite 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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Where is laffittite found?+
Is laffittite safe to handle?+
What rocks look like laffittite?+
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Find laffittite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
