Chloromagnesite is a rare, extremely deliquescent mineral formed primarily as a volcanic sublimate around fumaroles. Because it absorbs water rapidly from the atmosphere and dissolves, it must be stored in sealed, airtight containers to prevent it from turning into a liquid brine.
Is this chloromagnesite?
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 chloromagnesite with a known reference. Chloromagnesite sits at Mohs 1, 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.
- 5Look at form & habitCrystal system: trigonal. Typical habit: deliquescent, tastes bitter.
Often confused with
Chloromagnesite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside chloromagnesite
Minerals reported to co-occur with chloromagnesite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MgCl₂
- Mohs hardness
- 1
- Density
- 2.325 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Deliquescent, tastes bitter
- Cleavage
- Perfect basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Sublimate in fumaroles
Where rockhounds find chloromagnesite
Classic worldwide localities
- Vesuvius, Campania, Italy (type locality)
Field-hunting tip
Where it forms: Sublimate in fumaroles. If you start seeing hematite, tenorite, sylvite in float, you are in the right ground. Typical habit: deliquescent, tastes bitter. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify chloromagnesite?+
Where is chloromagnesite found?+
What rocks look like chloromagnesite?+
What minerals are found with chloromagnesite?+
What kind of rock does chloromagnesite form in?+
What is chloromagnesite used for?+
Find chloromagnesite on the map
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