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. Chloromagnesite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Chloromagnesite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: trigonal. Typical habit: hexagonal plates.
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
- 2.33 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Hexagonal Plates
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Fumaroles
- Typical price
- $50-300 per specimen
Where rockhounds find chloromagnesite
Classic worldwide localities
- Vesuvius, Italy
- Mount Etna, Italy
- Kamchatka, Russia
Field-hunting tip
Look in fumaroles country — that is the host setting where chloromagnesite typically forms. If you start seeing hematite, tenorite, sylvite in float, you are in the right ground. Field specimens usually show a hexagonal plates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify chloromagnesite?+
Where is chloromagnesite found?+
How much is chloromagnesite worth?+
What rocks look like chloromagnesite?+
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Find chloromagnesite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
