Natroalunite is a sodium-rich member of the Alunite group, typically found in low-temperature hydrothermal alteration environments. It often occurs as earthy or massive aggregates and is visually indistinguishable from standard alunite without chemical analysis.
Is this natroalunite?
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 natroalunite with a known reference. Natroalunite sits at Mohs 3.5-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Natroalunite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Natroalunite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, yellowish, colorless.
- 5Look at form & habitCrystal system: trigonal. Typical habit: massive, granular, or tabular crystals.
Often confused with
Natroalunite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside natroalunite
Minerals reported to co-occur with natroalunite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaAl₃(SO₄)₂(OH)₆
- Mohs hardness
- 3.5-4
- Density
- 2.7-2.9 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Massive, Granular, Or Tabular Crystals
- Cleavage
- Distinct On {0001}
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Hydrothermal Alteration Zones in Volcanic Rocks
- Typical price
- $10-60 for small specimens
Where rockhounds find natroalunite
Classic worldwide localities
- Italy
- USA
- Chile
- Russia
Field-hunting tip
Look in hydrothermal alteration zones in volcanic rocks country, the host setting where natroalunite typically forms. If you start seeing alunite, kaolinite, quartz in float, you are in the right ground. Field specimens usually show a massive, granular, or tabular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify natroalunite?+
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How much is natroalunite worth?+
What rocks look like natroalunite?+
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Find natroalunite on the map
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