Natropharmacoalumite is a rare secondary mineral typically occurring as small, transparent, pseudocubic crystals in the oxidized zones of arsenic-rich ore deposits. It is structurally related to the pharmacosiderite group and is most easily identified by its occurrence in specific secondary mineral assemblages alongside other arsenic-bearing species.
Is this natropharmacoalumite?
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 natropharmacoalumite with a known reference. Natropharmacoalumite 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: colorless.
- 5Look at form & habitCrystal system: cubic. Typical habit: pseudocubic crystals.
Often confused with
Natropharmacoalumite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside natropharmacoalumite
Minerals reported to co-occur with natropharmacoalumite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaAl₄(AsO₄)₃(OH)₄·4H₂O
- Mohs hardness
- 2.5
- Density
- 2.564 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous to adamantine
- Transparency
- Transparent
- Crystal system
- Cubic
- Crystal habit
- Pseudocubic crystals
- Cleavage
- Imperfect on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral in cavities and fractures in quartz in an epithermal gold-bearing alunite deposit
Where rockhounds find natropharmacoalumite
Classic worldwide localities
- Maria Josefa mine, in the Rodalquilar caldera, near Rodalquilar, Andalusia, Spain
Field-hunting tip
Where it forms: A secondary mineral in cavities and fractures in quartz in an epithermal gold-bearing alunite deposit. If you start seeing quartz, chenevixite, kaolinite 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 natropharmacoalumite?+
Where is natropharmacoalumite found?+
Is natropharmacoalumite safe to handle?+
What rocks look like natropharmacoalumite?+
What minerals are found with natropharmacoalumite?+
What kind of rock does natropharmacoalumite form in?+
What is natropharmacoalumite used for?+
Find natropharmacoalumite on the map
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