Hydroniumpharmacosiderite is a rare secondary mineral typically found in the oxidation zones of arsenic-bearing mineral deposits. It occurs as small, sharp, pseudocubic crystals that closely resemble standard pharmacosiderite but are distinguished primarily through chemical analysis or specialized X-ray diffraction due to the hydronium ion substitution.
Is this hydroniumpharmacosiderite?
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 hydroniumpharmacosiderite with a known reference. Hydroniumpharmacosiderite 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. Hydroniumpharmacosiderite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Hydroniumpharmacosiderite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, green, brown.
- 5Look at form & habitCrystal system: cubic. Typical habit: pseudocubic crystals, massive, granular.
Often confused with
Hydroniumpharmacosiderite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Hydroniumpharmacosiderite leaves yellow, Pharmacosiderite leaves white; luster reads vitreous on Hydroniumpharmacosiderite and adamantine on Pharmacosiderite.
How to tell apart: Scorodite is the harder of the two (Mohs 3.5-4 vs. 2.5); streak differs — Hydroniumpharmacosiderite leaves yellow, Scorodite leaves white; luster reads vitreous on Hydroniumpharmacosiderite and vitreous to sub-adamantine on Scorodite.
Often found alongside hydroniumpharmacosiderite
Minerals reported to co-occur with hydroniumpharmacosiderite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (H₃O)Fe₄(AsO₄)₃(OH)₄·4H₂O
- Mohs hardness
- 2.5
- Density
- 2.6-2.7 g/cm³
- Streak
- Yellow
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Cubic
- Crystal habit
- Pseudocubic Crystals, Massive, Granular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Arsenic-rich Hydrothermal Ore Deposits
- Typical price
- $20-150 thumbnail, $50-300 cabinet
Where rockhounds find hydroniumpharmacosiderite
Classic worldwide localities
- Cligga Head, Cornwall, England
- Mapimi, Durango, Mexico
- Black Pine Mine, Montana, USA
Field-hunting tip
Look in oxidized zones of arsenic-rich hydrothermal ore deposits country — that is the host setting where hydroniumpharmacosiderite typically forms. If you start seeing arsenopyrite, limonite, goethite in float, you are in the right ground. Field specimens usually show a pseudocubic crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify hydroniumpharmacosiderite?+
Where is hydroniumpharmacosiderite found?+
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