Alfredopetrovite is an extremely rare sulfate mineral identified by its occurrence in the oxidized zones of selenium-rich deposits. It typically forms small, clear, tabular crystals and is known for its distinct crystal chemistry within the copiapite group.
Is this alfredopetrovite?
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 alfredopetrovite with a known reference. Alfredopetrovite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless, blue.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: tabular to blocky crystals.
Often confused with
Alfredopetrovite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Alfredopetrovite leaves white, Copiapite leaves pale yellow; luster reads vitreous on Alfredopetrovite and pearly on {010} on Copiapite.
How to tell apart: Alunite is the harder of the two (Mohs 3.5-4 vs. 2.5).
Often found alongside alfredopetrovite
Minerals reported to co-occur with alfredopetrovite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al₂(SeO₃)₃·6H₂O
- Mohs hardness
- 2.5
- Density
- 2.504 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Tabular to blocky crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral in the weathered portions of a telethermal vein hosted by sandstones and shales
Where rockhounds find alfredopetrovite
Classic worldwide localities
- El Dragόn mine, Antonio Quijarro Province, Potosí Department, Bolivia
Field-hunting tip
Where it forms: A secondary mineral in the weathered portions of a telethermal vein hosted by sandstones and shales. If you start seeing ahlfeldite, allophane, calcite in float, you are in the right ground. Typical habit: tabular to blocky crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify alfredopetrovite?+
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Find alfredopetrovite on the map
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