Paraguanajuatite is a rare selenium-rich bismuth selenide typically found in hydrothermal vein deposits. It is best identified by its metallic lead-gray color, perfect cleavage, and distinct association with other bismuth-bearing minerals in volcanic or epithermal environments.
Is this paraguanajuatite?
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 paraguanajuatite with a known reference. Paraguanajuatite 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: gray.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: lead gray, yellowish white.
- 5Look at form & habitCrystal system: trigonal. Typical habit: inclusions.
Often confused with
Paraguanajuatite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Paraguanajuatite leaves gray, Tetradymite leaves pale steel-gray.
How to tell apart: Streak differs, so Paraguanajuatite leaves gray, Guanajuatite leaves shiny gray.
How to tell apart: Streak differs, so Paraguanajuatite leaves gray, Bismuthinite leaves lead-gray.
Often found alongside paraguanajuatite
Minerals reported to co-occur with paraguanajuatite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Bi₂Se₂Se
- Mohs hardness
- 2
- Density
- 6.2-7.0 g/cm³
- Colors
- Streak
- Gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Inclusions
- Cleavage
- Perfect on {0001}
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- Intergrown with guanajuatite in contact metamorphic as well as in hydrothermal veins (Santa Catarina mine, Mexico)
Where rockhounds find paraguanajuatite
Classic worldwide localities
- Guanajuato, in the Santa Catarina (type locality) and Leon mines, Mexico
- Falun, Kopparberg, Sweden
- Kawazu mine, Shizuoka Prefecture, Japan
Field-hunting tip
Where it forms: Intergrown with guanajuatite in contact metamorphic as well as in hydrothermal veins (Santa Catarina mine, Mexico). If you start seeing guanajuatite, bismuthinite, ferroselite in float, you are in the right ground. Typical habit: inclusions. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify paraguanajuatite?+
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Is paraguanajuatite safe to handle?+
What rocks look like paraguanajuatite?+
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Find paraguanajuatite on the map
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