Uchucchacuaite is a rare lead-silver-antimony sulfosalt known primarily from its type locality in Peru. It typically appears as metallic, lead-gray tabular crystals or as massive, granular aggregates within hydrothermal silver deposits.
Is this uchucchacuaite?
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 uchucchacuaite with a known reference. Uchucchacuaite sits at Mohs 3.5, 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: lead gray.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: anhedral grains, twinning common.
Often confused with
Uchucchacuaite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Uchucchacuaite is noticeably harder (Mohs 3.5 vs. 2.5-2.75); streak differs, so Uchucchacuaite leaves black, Galena leaves lead-gray.
How to tell apart: Streak differs, so Uchucchacuaite leaves black, Boulangerite leaves brownish.
How to tell apart: Uchucchacuaite is noticeably harder (Mohs 3.5 vs. 2.5); streak differs, so Uchucchacuaite leaves black, Jamesonite leaves black. grayish.
Often found alongside uchucchacuaite
Minerals reported to co-occur with uchucchacuaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AgMnPb₃Sb₅S₁₂
- Mohs hardness
- 3.5
- Density
- 5.16 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Anhedral grains, twinning common
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a telescoped polymetallic hydrothermal deposit (Peru)
Where rockhounds find uchucchacuaite
Classic worldwide localities
- Uchuc-Chacua deposit, Cajatambo Province, Peru (type locality)
- Hokkaido, Japan
Field-hunting tip
Where it forms: In a telescoped polymetallic hydrothermal deposit (Peru). If you start seeing alabandite, galena, benavidesite in float, you are in the right ground. Typical habit: anhedral grains, twinning common. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify uchucchacuaite?+
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What minerals are found with uchucchacuaite?+
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Find uchucchacuaite on the map
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