Chlorocalcite is a rare potassium calcium chloride mineral that typically forms as a fumarolic deposit or efflorescence. It is highly hygroscopic and requires careful storage in a dry environment to prevent it from deliquescing or dissolving due to atmospheric moisture.
Is this chlorocalcite?
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 chlorocalcite with a known reference. Chlorocalcite sits at Mohs 2.5-3, 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, light violet.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: deliquescent, pseudo cubic, tastes bitter.
Often confused with
Chlorocalcite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside chlorocalcite
Minerals reported to co-occur with chlorocalcite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KCaCl₃
- Mohs hardness
- 2.5-3
- Density
- 2.16 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Deliquescent, pseudo cubic, tastes bitter
- Cleavage
- In three nearly perpendicular directions, one direction better than the other two
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- As a sublimate in volcanic fumaroles (Vesuvius, Italy)
Where rockhounds find chlorocalcite
Classic worldwide localities
- Vesuvius, Campania, Italy
- Stassfurt, 34 km south of Magdeburg, Saxony-Anhalt, Germany
Field-hunting tip
Where it forms: As a sublimate in volcanic fumaroles (Vesuvius, Italy). If you start seeing sylvite, halite, hematite in float, you are in the right ground. Typical habit: deliquescent, pseudo cubic, tastes bitter. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify chlorocalcite?+
Where is chlorocalcite found?+
What rocks look like chlorocalcite?+
What minerals are found with chlorocalcite?+
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Find chlorocalcite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
