Fettelite is an extremely rare silver-arsenic sulfosalt often found in association with other silver minerals in hydrothermal deposits. Collectors should look for its distinctive dark red to black metallic appearance and perfect basal cleavage in small, tabular specimens.
Is this fettelite?
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 fettelite with a known reference. Fettelite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Fettelite leaves a dark red streak.
- 3Read the lusterHold the specimen under a strong light. Fettelite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: dark red, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, massive, coatings.
Often confused with
Fettelite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Fettelite leaves dark red, Proustite leaves scarlet; luster reads metallic on Fettelite and adamantine on Proustite.
How to tell apart: Streak differs — Fettelite leaves dark red, Pyrargyrite leaves red; luster reads metallic on Fettelite and metallic to adamantine on Pyrargyrite.
Often found alongside fettelite
Minerals reported to co-occur with fettelite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ag₁₇As₂S₁₁
- Mohs hardness
- 2.5
- Density
- 6.32 g/cm³
- Streak
- Dark Red
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Massive, Coatings
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Silver-rich Veins
- Typical price
- $100-500 thumbnail, $500+ cabinet
Where rockhounds find fettelite
Classic worldwide localities
- Chañarcillo, Chile
- St. Andreasberg, Germany
Field-hunting tip
Look in hydrothermal silver-rich veins country — that is the host setting where fettelite typically forms. If you start seeing proustite, pearceite, silver in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, coatings habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find fettelite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
