Ghiaraite is a rare calcium oxide that forms milky white to light gray intergrown equant grains. It occurs in volcanic ejecta on the surface of a lava flow. Associated minerals include chlorocalcite, hematite and sylvite. It was first described from Massa di Somma, Vesuvius, Italy.
Is this ghiaraite?
3-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 ghiaraite with a known reference. Ghiaraite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Match the color rangeCompare against the expected color range: milky white.
- 3Look at form & habitCrystal system: triclinic. Typical habit: intergrown equant grains.
Often confused with
Ghiaraite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside ghiaraite
Minerals reported to co-occur with ghiaraite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaCl₂·4H₂O
- Mohs hardness
- 2
- Density
- 1.826 g/cm³
- Colors
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Intergrown equant grains
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In volcanic ejecta on the surface of a lava flow
Where rockhounds find ghiaraite
Classic worldwide localities
- Massa di Somma, Vesuvius, Italy
Field-hunting tip
Where it forms: In volcanic ejecta on the surface of a lava flow. If you start seeing chlorocalcite, hematite, sylvite in float, you are in the right ground. Typical habit: intergrown equant grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ghiaraite?+
Where is ghiaraite found?+
What rocks look like ghiaraite?+
What minerals are found with ghiaraite?+
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Find ghiaraite on the map
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