Cerromojonite is a rare copper lead bismuth selenide that forms black type I: as grains. It was approved as a distinct mineral species in 2018. It was first described from the El Dragón mine, Province of Antonio Quijarro, Department of Potosí, Bolivia.
Is this cerromojonite?
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 cerromojonite with a known reference. Cerromojonite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black, gray to cream-white in reflected light.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: type I: as grains.
Often confused with
Cerromojonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Cerromojonite leaves black, gray to cream-white in reflected light, Galena leaves lead-gray.
How to tell apart: Streak differs, so Cerromojonite leaves black, gray to cream-white in reflected light, Bournonite leaves steel-gray to iron-black; luster reads metallic on Cerromojonite and brilliant to dull on Bournonite.
Often found alongside cerromojonite
Minerals reported to co-occur with cerromojonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuPbBiSe₃
- Mohs hardness
- 2
- Density
- 7.035 g/cm³
- Colors
- Streak
- Black, gray to cream-white in reflected light
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Type I: as grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a vein in a shear zone cutting a series of thinly stratified, pyrite-rich black shales, and reddish-gray, hematite-bearing siltstones
Where rockhounds find cerromojonite
Classic worldwide localities
- El Dragón mine, ~30 km southwest of Cerro Rico de Potosí, Province of Antonio Quijarro, Department of Potosí, Bolivia
Field-hunting tip
Where it forms: In a vein in a shear zone cutting a series of thinly stratified, pyrite-rich black shales, and reddish-gray, hematite-bearing siltstones. If you start seeing quijarroite, penroseite, klockmannite in float, you are in the right ground. Typical habit: type I: as grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cerromojonite?+
Where is cerromojonite found?+
Is cerromojonite safe to handle?+
What rocks look like cerromojonite?+
What minerals are found with cerromojonite?+
What kind of rock does cerromojonite form in?+
What is cerromojonite used for?+
Find cerromojonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
