Santite is a rare potassium borate mineral typically found as white, granular encrustations within geothermal environments. It is highly soluble in water and unstable in humid air, making it a challenging species for collectors to preserve. It is primarily identified by its association with borate-rich fumaroles in Italy.
Is this santite?
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 santite with a known reference. Santite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Santite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Santite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: granular to compact aggregates.
Often confused with
Santite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside santite
Minerals reported to co-occur with santite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K[B₅O₆(OH)₄]·2H₂O
- Mohs hardness
- 2
- Density
- 2.16 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Granular to Compact Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Geothermal Fumarole Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find santite
Classic worldwide localities
- Sasso Pisano, Tuscany, Italy
- Larderello, Tuscany, Italy
Field-hunting tip
Look in geothermal fumarole deposits country — that is the host setting where santite typically forms. If you start seeing sassolite, borax in float, you are in the right ground. Field specimens usually show a granular to compact aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find santite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
