Hydroniumpharmacoalumite is a rare secondary mineral typically found in the oxidized zones of arsenic-bearing ore deposits. It occurs as small, delicate, often pseudocubic crystals that closely resemble members of the pharmacosiderite group.
Is this hydroniumpharmacoalumite?
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 hydroniumpharmacoalumite with a known reference. Hydroniumpharmacoalumite 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 to adamantine.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: cubic. Typical habit: pseudocubic crystals.
Often confused with
Hydroniumpharmacoalumite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Hydroniumpharmacoalumite leaves white, Pharmacosiderite leaves yellowish green; luster reads vitreous to adamantine on Hydroniumpharmacoalumite and adamantine to greasy on Pharmacosiderite.
Often found alongside hydroniumpharmacoalumite
Minerals reported to co-occur with hydroniumpharmacoalumite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (H₃O)Al₄(AsO₄)₃(OH)₄·4.5H₂O
- Mohs hardness
- ~2.5
- Density
- 2.486 g/cm³
- Streak
- White
- Luster
- Vitreous to adamantine
- Transparency
- Transparent
- Crystal system
- Cubic
- Crystal habit
- Pseudocubic crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary oxidation product of arsenic-bearing minerals in fractures of alunitized gold-bearing volcanic rocks
Where rockhounds find hydroniumpharmacoalumite
Classic worldwide localities
- Maria Josefa gold mine, near Rodalquilar, Andalusia region, Spain
Field-hunting tip
Where it forms: A secondary oxidation product of arsenic-bearing minerals in fractures of alunitized gold-bearing volcanic rocks. If you start seeing pharmacoalumite, pharmacosiderite, natropharmacosiderite in float, you are in the right ground. Typical habit: pseudocubic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify hydroniumpharmacoalumite?+
Where is hydroniumpharmacoalumite found?+
Is hydroniumpharmacoalumite safe to handle?+
What rocks look like hydroniumpharmacoalumite?+
What minerals are found with hydroniumpharmacoalumite?+
What kind of rock does hydroniumpharmacoalumite form in?+
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