Sassolite is a rare, water-soluble mineral that typically forms as white, scaly crusts or tabular crystals around volcanic fumaroles. It is best identified by its pearly luster and soft, soapy feel, though collectors must store it in dry environments to prevent dissolution due to its extreme solubility in water.
Is this sassolite?
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 sassolite with a known reference. Sassolite sits at Mohs 1 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Sassolite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Sassolite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, yellowish, gray.
- 5Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals, scaly or crusty masses.
Often confused with
Sassolite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside sassolite
Minerals reported to co-occur with sassolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- H₃BO₃
- Mohs hardness
- 1
- Density
- 1.44 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Tabular Crystals, Scaly or Crusty Masses
- Cleavage
- Perfect Basal
- Rarity
- Uncommon
- Uses
- Collector, Chemical Industry
- Host rock
- Fumaroles and Solfataras of Volcanic Regions
- Typical price
- $10-50 per specimen
Where rockhounds find sassolite
Classic worldwide localities
- Tuscany, Italy
- Lipari Islands, Italy
- Vulcano, Italy
- Steiermark, Austria
Field-hunting tip
Look in fumaroles and solfataras of volcanic regions country — that is the host setting where sassolite typically forms. If you start seeing sulfur, gypsum, alunogen in float, you are in the right ground. Field specimens usually show a tabular crystals, scaly or crusty masses habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find sassolite on the map
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