Natropharmacosiderite is a rare secondary mineral found in the oxidation zones of arsenic-bearing ore deposits. It typically forms small, sharp, bright green cubic crystals that are prized by mineral collectors for their vibrant color and geometric perfection.
Is this natropharmacosiderite?
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 natropharmacosiderite with a known reference. Natropharmacosiderite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: pale green, dull orange.
- 5Look at form & habitCrystal system: cubic. Typical habit: cubic crystals.
Often confused with
Natropharmacosiderite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Natropharmacosiderite leaves pale yellow, Pharmacosiderite leaves yellowish green; luster reads vitreous on Natropharmacosiderite and adamantine to greasy on Pharmacosiderite.
How to tell apart: Streak differs, so Natropharmacosiderite leaves pale yellow, Scorodite leaves greenish white.
Often found alongside natropharmacosiderite
Minerals reported to co-occur with natropharmacosiderite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaFe₄(AsO₄)₃(OH)₄·4H₂O
- Mohs hardness
- 3
- Density
- 2.79 g/cm³
- Colors
- Pale greenDull orange
- Streak
- Pale yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Cubic
- Crystal habit
- Cubic crystals
- Cleavage
- Imperfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Found on a museum specimen, presumably an alteration product of arsenopyrite
Where rockhounds find natropharmacosiderite
Classic worldwide localities
- Marda, Western Australia (type locality)
Field-hunting tip
Where it forms: Found on a museum specimen, presumably an alteration product of arsenopyrite. If you start seeing arsenopyrite, limonite, scorodite in float, you are in the right ground. Typical habit: cubic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify natropharmacosiderite?+
Where is natropharmacosiderite found?+
Is natropharmacosiderite safe to handle?+
What rocks look like natropharmacosiderite?+
What minerals are found with natropharmacosiderite?+
What kind of rock does natropharmacosiderite form in?+
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Find natropharmacosiderite on the map
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