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?
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 ghiaraite with a known reference. Ghiaraite 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. Ghiaraite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Ghiaraite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: milky white, light gray.
- 5Look 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
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Intergrown Equant Grains
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Volcanic Fumaroles
Where rockhounds find ghiaraite
Classic worldwide localities
- Vesuvius, Italy
Field-hunting tip
Look in volcanic fumaroles country, the host setting where ghiaraite typically forms. If you start seeing fluorite, glauberite, halite in float, you are in the right ground. Field specimens usually show a intergrown equant grains habit, so 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?+
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Find ghiaraite on the map
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