Cesanite is a rare sodium-calcium sulfate mineral that was first discovered in volcanic deposits near Cesan, Italy. It typically forms as small, colorless to white prismatic crystals and is prized by mineralogists for its rarity and structural relationship to the apatite group.
Is this cesanite?
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 cesanite with a known reference. Cesanite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: greasy to silky in aggregates.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: prismatic crystals.
Often confused with
Cesanite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Apatite is the harder of the two (Mohs 5 vs. 2-3); luster reads greasy to silky in aggregates on Cesanite and vitreous on Apatite.
How to tell apart: Luster reads greasy to silky in aggregates on Cesanite and pearly on {010}, vitreous to greasy on {001}; vitreous on {100} on Anhydrite.
Often found alongside cesanite
Minerals reported to co-occur with cesanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Na₃(SO₄)₃OH
- Mohs hardness
- 2-3
- Density
- 2.786 g/cm³
- Streak
- White
- Luster
- Greasy to silky in aggregates
- Transparency
- Transparent to translucent
- Crystal system
- Hexagonal
- Crystal habit
- Prismatic crystals
- Cleavage
- On {0001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As vein and cavity fillings in brecciated rock in an active geothermal field
Where rockhounds find cesanite
Classic worldwide localities
- Core samples from the Cesano-I geothermal well, Cesano area, Latium, Italy (type locality)
Field-hunting tip
Where it forms: As vein and cavity fillings in brecciated rock in an active geothermal field. If you start seeing görgeyite, pyrite, gypsum in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find cesanite on the map
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