Pharmacoalumite is a rare secondary arsenic mineral that typically forms small, pseudocubic crystals in the oxidized zones of ore deposits. It is chemically similar to pharmacosiderite but features aluminum instead of iron in its structure, resulting in lighter, often yellowish or greenish hues.
Is this pharmacoalumite?
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 pharmacoalumite with a known reference. Pharmacoalumite 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. Pharmacoalumite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Pharmacoalumite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, yellow, pale green.
- 5Look at form & habitCrystal system: cubic. Typical habit: pseudocubic crystals, crusts, or massive.
Often confused with
Pharmacoalumite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside pharmacoalumite
Minerals reported to co-occur with pharmacoalumite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KAl₄(AsO₄)₃(OH)₄·6H₂O
- Mohs hardness
- 2.5
- Density
- 2.4-2.5 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Cubic
- Crystal habit
- Pseudocubic Crystals, Crusts, Or Massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Arsenic-rich Hydrothermal Deposits
- Typical price
- $20-150 for micro-to-thumbnail specimens
Where rockhounds find pharmacoalumite
Classic worldwide localities
- Germany
- United Kingdom
- USA
- France
Field-hunting tip
Look in oxidized zones of arsenic-rich hydrothermal deposits country — that is the host setting where pharmacoalumite typically forms. If you start seeing pharmacosiderite, scorodite, arsenopyrite in float, you are in the right ground. Field specimens usually show a pseudocubic crystals, crusts, or massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify pharmacoalumite?+
Where is pharmacoalumite found?+
How much is pharmacoalumite worth?+
Is pharmacoalumite safe to handle?+
What rocks look like pharmacoalumite?+
What minerals are found with pharmacoalumite?+
What kind of rock does pharmacoalumite form in?+
What is pharmacoalumite used for?+
Find pharmacoalumite on the map
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