Chloraluminite is a rare hydrated aluminum chloride mineral typically found as white, efflorescent crusts or fine crystalline coatings around volcanic fumaroles. Due to its high solubility in water and sensitivity to atmospheric humidity, it is extremely fragile and must be stored in a dry, sealed container to prevent deliquescence.
Is this chloraluminite?
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 chloraluminite with a known reference. Chloraluminite sits at Mohs 2.5, 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: vitreous.
- 4Match the color rangeCompare against the expected color range: white, colorless, yellowish white.
- 5Look at form & habitCrystal system: trigonal. Typical habit: crusts, efflorescent growths.
Often confused with
Chloraluminite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside chloraluminite
Minerals reported to co-occur with chloraluminite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AlCl₃·6H₂O
- Mohs hardness
- 2.5
- Density
- 1.644 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Crusts, efflorescent growths
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As crusts around acidic fumaroles (Vesuvius, Italy)
Where rockhounds find chloraluminite
Classic worldwide localities
- Vesuvius, Campania, Italy
- Cerro Pintados, 80 km southeast of Iquique, Tarapacá, Chile
- Parícutin volcano, Michoacán, Mexico
Field-hunting tip
Where it forms: As crusts around acidic fumaroles (Vesuvius, Italy). If you start seeing molysite, chloromagnesite, natroalunite in float, you are in the right ground. Typical habit: crusts, efflorescent growths. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify chloraluminite?+
Where is chloraluminite found?+
What rocks look like chloraluminite?+
What minerals are found with chloraluminite?+
What kind of rock does chloraluminite form in?+
What is chloraluminite used for?+
Find chloraluminite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
