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.

Hardness

1.5-2

Mohs

Luster

Metallic

Streak

Grayish-black

Transparency

Opaque

mineralrare

Tsumoite

Hardness: 1.5-2
Luster: Metallic
Streak: Grayish-black
Transparency: Opaque

Is this tsumoite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch tsumoite with a known reference. Tsumoite sits at Mohs 1.5-2, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Tsumoite leaves a grayish-black streak.
3
Read the luster
Hold the specimen under a strong light. Tsumoite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: white, lead-gray.
5
Look at form & habit
Crystal system: trigonal. Typical habit: lamellar to granular aggregates.

Often confused with

Tsumoite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Tellurobismuthite

Mohs 1.5-2

How to tell apart: Streak differs, so Tsumoite leaves grayish-black, Tellurobismuthite leaves lead-gray.

How to tell apart: Streak differs, so Tsumoite leaves grayish-black, Tetradymite leaves lead-gray.

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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: 1.5-2
Density: 8.32 g/cm³
Colors: White Lead-gray
Streak: Grayish-black
Luster: Metallic
Transparency: Opaque
Crystal system: Trigonal
Crystal habit: Lamellar to Granular Aggregates
Cleavage: Perfect Basal
Rarity: Rare
Uses: Collector
Host rock: Skarn Deposits
Typical price: $50-300 per small specimen

Where rockhounds find tsumoite

Classic worldwide localities

Tsumo Mine, Japan
Dashkesan, Azerbaijan
Guanajuato, Mexico
Kalguty, Russia

Field-hunting tip

Look in skarn deposits country, the host setting where tsumoite typically forms. If you start seeing bismuthinite, chalcopyrite, pyrite in float, you are in the right ground. Field specimens usually show a lamellar to granular aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tsumoite?+

Mohs hardness is 1.5-2. It typically shows a metallic luster. The streak is grayish-black. Common colors include white, lead-gray.

Where is tsumoite found?+

Notable localities include Tsumo Mine, Japan; Dashkesan, Azerbaijan; Guanajuato, Mexico; Kalguty, Russia.

How much is tsumoite worth?+

Typical asking prices fall in the range of $50-300 per small specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is tsumoite safe to handle?+

It contains toxic constituents. Contains tellurium and bismuth; handle with care and wash hands thoroughly after handling to avoid ingestion or skin absorption of dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like tsumoite?+

Tsumoite is most often confused with Tellurobismuthite, Tetradymite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with tsumoite?+

Tsumoite commonly co-occurs with Bismuthinite, Chalcopyrite, Pyrite, Scheelite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tsumoite form in?+

Tsumoite typically forms in skarn deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tsumoite used for?+

Tsumoite is used in collector.

Find tsumoite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.