Antarcticite is an extremely rare and hygroscopic calcium chloride hexahydrate that typically forms in hyper-saline environments. Because it dissolves rapidly in humid air, specimens must be stored in airtight, sealed containers to prevent them from deliquescing into a liquid. It is most frequently found as delicate, needle-like crystals in extreme desert climates or saline lake beds.
Is this antarcticite?
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 antarcticite with a known reference. Antarcticite sits at Mohs 2-3, 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: colorless.
- 5Look at form & habitCrystal system: trigonal. Typical habit: acicular, crystalline, deliquescent.
Often confused with
Antarcticite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside antarcticite
Minerals reported to co-occur with antarcticite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaCl₂·6H₂O
- Mohs hardness
- 2-3
- Density
- 1.715 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Acicular, crystalline, deliquescent
- Cleavage
- {0001}, perfect; one prismatic, good to perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A precipitate from highly saline brines under very arid conditions (Don Juan Pond, Antarctica; Bristol Dry Lake, California, USA)
Where rockhounds find antarcticite
Classic worldwide localities
- Bristol Dry Lake, San Bernardino Co., California, USA
- Don Juan Pond, Wright Valley, around Mt. Erebus, Victoria Land, Antarctica
- North Andros Island, Bahamas
- Bushveld complex, on Driekop Farm, Transvaal, South Africa
Field-hunting tip
Where it forms: A precipitate from highly saline brines under very arid conditions (Don Juan Pond, Antarctica; Bristol Dry Lake, California, USA). If you start seeing halite, gypsum, celestine in float, you are in the right ground. Typical habit: acicular, crystalline, deliquescent. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify antarcticite?+
Where is antarcticite found?+
What rocks look like antarcticite?+
What minerals are found with antarcticite?+
What kind of rock does antarcticite form in?+
What is antarcticite used for?+
Find antarcticite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
