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, so 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, so 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, 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?+
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