Tetradymite is a distinct telluride mineral recognized by its metallic luster and perfect basal cleavage, often forming foliated, platy masses that resemble molybdenite. It is most commonly found in hydrothermal gold-bearing veins and contact metamorphic skarns. Collectors should look for its characteristic steel-gray color and sectile nature.
Is this tetradymite?
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 tetradymite with a known reference. Tetradymite 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: pale steel-gray.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic, splendent on fresh surfaces.
- 4Match the color rangeCompare against the expected color range: steel gray, yellow gray.
- 5Look at form & habitCrystal system: trigonal. Typical habit: granular, lamellar, pseudo hexagonal.
Often confused with
Tetradymite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Tetradymite leaves pale steel-gray, Molybdenite leaves bluish gray.
How to tell apart: Streak differs, so Tetradymite leaves pale steel-gray, Bismuthinite leaves lead-gray.
Often found alongside tetradymite
Minerals reported to co-occur with tetradymite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Bi₂Te₂S
- Mohs hardness
- 1.5-2
- Density
- 7.3 g/cm³
- Colors
- Streak
- Pale steel-gray
- Luster
- Metallic, splendent on fresh surfaces
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Granular, lamellar, pseudo hexagonal
- Cleavage
- Perfect on {0001}
- Rarity
- Uncommon
- Uses
- Collector, Ore of tellurium
- Host rock
- In hydrothermal gold-quartz veins of medium to high temperature of formation; also in contact metamorphic deposits
Where rockhounds find tetradymite
2 mapped spotsClassic worldwide localities
- Trail Creek, Blaine Co., Idaho, USA
- Sylvanite district, Hidalgo Co., New Mexico, USA
- Whitehall mines, Spotsylvania Co., Virginia, USA
- Žubkov (Schubkau) (type locality), as fine twinned crystals, Slovakia
- Băiţa (Rezbánya), also Ciclova, Moraviţa (Moravicza), and Oraviţa (Oravicza), Romania
- Narverud and Seljord, Norway
Field-hunting tip
Where it forms: In hydrothermal gold-quartz veins of medium to high temperature of formation; also in contact metamorphic deposits. If you start seeing tellurium, tellurobismuthite, gold in float, you are in the right ground. Typical habit: granular, lamellar, pseudo hexagonal. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Mexico, North Carolina. Start trip planning there.
Common questions
How do you identify tetradymite?+
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Can I find tetradymite in the United States?+
Is tetradymite safe to handle?+
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Find tetradymite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
