Pharmacolite is a secondary arsenic-bearing mineral typically found as delicate acicular crystals or tufted, fibrous crusts. It commonly occurs in the oxidation zones of ore deposits where arsenic minerals have been weathered. Due to its arsenic content, collectors should handle it with care and store it in enclosed containers.
Is this pharmacolite?
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 pharmacolite with a known reference. Pharmacolite 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. Pharmacolite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Pharmacolite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, grayish.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular, fibrous, botryoidal, crusts.
Often confused with
Pharmacolite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside pharmacolite
Minerals reported to co-occur with pharmacolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaH(AsO₄)·2H₂O
- Mohs hardness
- 2-2.5
- Density
- 2.6-2.7 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular, Fibrous, Botryoidal, Crusts
- Cleavage
- Perfect
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Oxidized Zones of Arsenic-rich Hydrothermal Veins
- Typical price
- $10-100 per specimen depending on size and quality
Where rockhounds find pharmacolite
Classic worldwide localities
- Jáchymov, Czech Republic
- Schneeberg, Germany
- Ste. Marie-aux-Mines, France
- Cornwall, England
Field-hunting tip
Look in oxidized zones of arsenic-rich hydrothermal veins country — that is the host setting where pharmacolite typically forms. If you start seeing arsenopyrite, proustite, annabergite in float, you are in the right ground. Field specimens usually show a acicular, fibrous, botryoidal, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find pharmacolite on the map
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