Petříčekite is a rare copper selenide mineral typically found in hydrothermal vein deposits. It is often identified by its metallic luster and association with other selenide species in rare-mineral localities.
Is this petříčekite?
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 petříčekite with a known reference. Petříčekite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 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: prismatic crystals.
Often confused with
Petříčekite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Löllingite is the harder of the two (Mohs 5-5.5 vs. 2-2.5); streak differs, so Petříčekite leaves black, Löllingite leaves grayish black.
How to tell apart: Marcasite is the harder of the two (Mohs 6-6.5 vs. 2-2.5); streak differs, so Petříčekite leaves black, Marcasite leaves grayish or brownish black.
Often found alongside petříčekite
Minerals reported to co-occur with petříčekite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuSe₂
- Mohs hardness
- 2-2.5
- Density
- 6.673 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In low-temperature hydrothermal veins cutting metamorphic rocks near the contact with a granitoid pluton (Czech Republic); a late-stage mineral in hydrothermal veinlets cutting black shale and siltstone (Bolivia)
Where rockhounds find petříčekite
Classic worldwide localities
- Předbořice uranium deposit, Central Bohemia Region, Czech Republic; at the El Dragón mine, Potosi, Bolivia and at Sierra de Cacheuta, Luján de Cuyo Department, Mendoza, Argentina
Field-hunting tip
Where it forms: In low-temperature hydrothermal veins cutting metamorphic rocks near the contact with a granitoid pluton (Czech Republic); a late-stage mineral in hydrothermal veinlets cutting black shale and siltstone (Bolivia). If you start seeing eucairite, tiemannite, eskebornite in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find petříčekite on the map
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