Bismutite is a secondary mineral that typically forms as an oxidation product of native bismuth or bismuthinite. It is most commonly found as earthy, yellowish to white crusts or coatings, making identification often reliant on chemical tests or location context rather than distinct crystal forms.
Is this bismutite?
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 bismutite with a known reference. Bismutite sits at Mohs 2.5-3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: gray.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous, waxy, may be dull to earthy.
- 4Match the color rangeCompare against the expected color range: yellow, brown, brownish yellow, green, gray.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: earthy, fibrous.
Often confused with
Bismutite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside bismutite
Minerals reported to co-occur with bismutite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Bi₂O₂CO₃
- Mohs hardness
- 2.5-3.5
- Density
- 7 g/cm³
- Streak
- Gray
- Luster
- Vitreous, waxy, may be dull to earthy
- Transparency
- Opaque to transparent in small grains
- Crystal system
- Tetragonal
- Crystal habit
- Earthy, fibrous
- Cleavage
- On {001}, probable
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- A relatively common alteration product of other bismuth-bearing minerals in hydrothermal mineral deposits and granite pegmatites
Where rockhounds find bismutite
3 mapped spotsClassic worldwide localities
- Harding mine, Dixon, Taos Co., New Mexico, USA
- Trout Creek Pass pegmatites, Chaffee Co., Colorado, USA
- Comstock mine, Dos Cabezos Mountains, Cochise Co., Arizona, USA
- Mammoth mine, Tintic district, Juab Co., Utah, USA
- Ullersreuth, Thuringia, Germany
- Schneeberg, Johanngeorgenstadt, Saxony, Germany
Field-hunting tip
Where it forms: A relatively common alteration product of other bismuth-bearing minerals in hydrothermal mineral deposits and granite pegmatites. If you start seeing bismuth, bismuthinite, tetradymite in float, you are in the right ground. Typical habit: earthy, fibrous. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Colorado, Utah, Wyoming. Start trip planning there.
Common questions
How do you identify bismutite?+
Where is bismutite found?+
Can I find bismutite in the United States?+
What rocks look like bismutite?+
What minerals are found with bismutite?+
What kind of rock does bismutite form in?+
What is bismutite used for?+
Find bismutite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
