Tsumoite is a rare bismuth telluride mineral typically found in skarn environments. Collectors should look for its metallic, lead-gray appearance and distinct perfect cleavage, often occurring as small inclusions or grains within other sulfide minerals.
Is this tsumoite?
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 tsumoite with a known reference. Tsumoite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: steel-gray.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: silver white.
- 5Look at form & habitCrystal system: trigonal. Typical habit: aggregates, irregular grains.
Often confused with
Tsumoite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside tsumoite
Minerals reported to co-occur with tsumoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- BiTe
- Mohs hardness
- 2.5-3
- Density
- 8.16 g/cm³
- Colors
- Streak
- Steel-gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Aggregates, irregular grains
- Cleavage
- Perfect on {0001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In massive Ni–Cu–PGE deposits; in Cu–Zn–Pb deposits, with sulfosalts, formed at lower temperatures
Where rockhounds find tsumoite
Classic worldwide localities
- Sylvanite, Hidalgo Co., New Mexico, USA
- Tsumo mine, about 50 km northwest of Hiroshima City, Shimane Prefecture (type locality), Japan
- Dashuigou tellurium deposit, Sichuan Province, China
- Ban Phuc deposit, northwestern Vietnam
- Kolar Gold Fields, Karnataka, India
- Tyrnyauz W–Mo deposit, left bank of the Baksan River Valley, northern Caucasus Mountains, Russia
Field-hunting tip
Where it forms: In massive Ni–Cu–PGE deposits; in Cu–Zn–Pb deposits, with sulfosalts, formed at lower temperatures. If you start seeing pentlandite, chalcopyrite, pyrrhotite in float, you are in the right ground. Typical habit: aggregates, irregular grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify tsumoite?+
Where is tsumoite found?+
Is tsumoite safe to handle?+
What rocks look like tsumoite?+
What minerals are found with tsumoite?+
What kind of rock does tsumoite form in?+
What is tsumoite used for?+
Find tsumoite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
