Tillmannsite is a very rare mercury-silver telluride mineral typically found as microscopic grains within hydrothermal ore deposits. It is best identified through laboratory analysis of metallic phases in polished sections, as it rarely forms distinct macroscopic crystals.
Is this tillmannsite?
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 tillmannsite with a known reference. Tillmannsite 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. Tillmannsite leaves a brownish red streak.
- 3Read the lusterHold the specimen under a strong light. Tillmannsite typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: red, brownish red.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: anhedral grains.
Often confused with
Tillmannsite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Tillmannsite leaves brownish red, Tetrahedrite leaves black; luster reads adamantine on Tillmannsite and metallic on Tetrahedrite.
How to tell apart: Streak differs, so Tillmannsite leaves brownish red, Goldfieldite leaves black; luster reads adamantine on Tillmannsite and metallic on Goldfieldite.
Often found alongside tillmannsite
Minerals reported to co-occur with tillmannsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ag₃HgTe₄
- Mohs hardness
- 3.5
- Density
- 8.55 g/cm³
- Colors
- Streak
- Brownish Red
- Luster
- Adamantine
- Transparency
- Translucent
- Crystal system
- Tetragonal
- Crystal habit
- Anhedral Grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
Where rockhounds find tillmannsite
Classic worldwide localities
- Old copper mines at Roua, Alpes-Maritimes, France
Field-hunting tip
Look in hydrothermal veins country, the host setting where tillmannsite typically forms. If you start seeing quartz, galena, pyrite in float, you are in the right ground. Field specimens usually show a anhedral grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find tillmannsite on the map
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