Rauenthalite is a very rare secondary arsenic mineral that typically occurs as delicate, white acicular crystal sprays or coatings in hydrothermal veins. It is named after its primary type locality in the Rauenthal valley of France and is frequently found alongside other secondary arsenic species. Due to its solubility and fragility, it is a specialized collector's mineral that requires careful handling.
Is this rauenthalite?
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 rauenthalite with a known reference. Rauenthalite 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. Rauenthalite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Rauenthalite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: triclinic. Typical habit: acicular crystals, radiating sprays, crusts.
Often confused with
Rauenthalite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside rauenthalite
Minerals reported to co-occur with rauenthalite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₃(AsO₄)₂·10H₂O
- Mohs hardness
- 2
- Density
- 2.47 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Acicular Crystals, Radiating Sprays, Crusts
- Cleavage
- Perfect On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
- Typical price
- $50-300 per specimen depending on size and quality
Where rockhounds find rauenthalite
Classic worldwide localities
- Rauenthal, Sainte-Marie-aux-Mines, France
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where rauenthalite typically forms. If you start seeing pharmacolite, picropharmacolite, arsenolite in float, you are in the right ground. Field specimens usually show a acicular crystals, radiating sprays, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find rauenthalite on the map
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