Aphthitalite is a rare sulfate mineral that typically forms as white or colorless crusts around volcanic fumaroles or within saline evaporite deposits. Collectors should handle these specimens with care, as they are highly water-soluble and must be stored in dry, climate-controlled environments to prevent degradation.
Is this aphthitalite?
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 aphthitalite with a known reference. Aphthitalite sits at Mohs 3-3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Aphthitalite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Aphthitalite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, gray, blue, green.
- 5Look at form & habitCrystal system: trigonal. Typical habit: tabular crystals, crusts, efflorescences.
Often confused with
Aphthitalite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside aphthitalite
Minerals reported to co-occur with aphthitalite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (K,Na)₃Na(SO₄)₂
- Mohs hardness
- 3-3.5
- Density
- 2.65 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Tabular Crystals, Crusts, Efflorescences
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector, Scientific Research
- Host rock
- Volcanic Fumaroles, Evaporite Deposits
- Typical price
- $20-100 per specimen depending on size and quality
Where rockhounds find aphthitalite
1 mapped spotsClassic worldwide localities
- Mount Vesuvius, Italy
- Etna, Italy
- Searles Lake, USA
- Solikamsk, Russia
Field-hunting tip
Look in volcanic fumaroles, evaporite deposits country — that is the host setting where aphthitalite typically forms. If you start seeing thenardite, halite, sylvite in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts, efflorescences habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in California — start trip planning there.
Common questions
How do you identify aphthitalite?+
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How much is aphthitalite worth?+
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Find aphthitalite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
