Allochalcoselite is an extremely rare copper-lead-bismuth selenide mineral. It is primarily identified from the Predborice hydrothermal veins in the Czech Republic where it occurs in minute quantities associated with other selenide minerals.
Is this allochalcoselite?
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 allochalcoselite with a known reference. Allochalcoselite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: dark brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: encrustations.
Often confused with
Allochalcoselite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Allochalcoselite leaves brown, Clausthalite leaves grayish black; luster reads adamantine on Allochalcoselite and metallic on Clausthalite.
How to tell apart: Streak differs, so Allochalcoselite leaves brown, Berzelianite leaves shining; luster reads adamantine on Allochalcoselite and metallic on Berzelianite.
Often found alongside allochalcoselite
Minerals reported to co-occur with allochalcoselite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuCu₅PbO₂(SeO₃)₂Cl₅
- Mohs hardness
- 3-4
- Density
- 4.61 g/cm³
- Colors
- Streak
- Brown
- Luster
- Adamantine
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Encrustations
- Cleavage
- Perfect on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Formed by sublimation around a degassing volcanic fumarole
Where rockhounds find allochalcoselite
Classic worldwide localities
- Second cinder cone of the northern breach of the Great Tolbachik Fissure Eruption, Kamchatka Region, Russia (type locality)
Field-hunting tip
Where it forms: Formed by sublimation around a degassing volcanic fumarole. If you start seeing cotunnite, sophiite, ilinskite in float, you are in the right ground. Typical habit: encrustations. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify allochalcoselite?+
Where is allochalcoselite found?+
Is allochalcoselite safe to handle?+
What rocks look like allochalcoselite?+
What minerals are found with allochalcoselite?+
What kind of rock does allochalcoselite form in?+
What is allochalcoselite used for?+
Find allochalcoselite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
