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 — that is 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?+
Where is natroalunite found?+
How much is natroalunite worth?+
What rocks look like natroalunite?+
What minerals are found with natroalunite?+
What kind of rock does natroalunite form in?+
What is natroalunite used for?+
Find natroalunite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
