Antarcticite is an uncommon calcium chloride hexahydrate mineral with formula: CaCl2·6H2O. It forms colorless acicular trigonal crystals. It is hygroscopic of 1.715.
As its name implies, it was first described in 1965 for an occurrence in Antarctica where it occurs as crystalline precipitate in Don Juan Pond, Victoria Land. This discovery was made by Japanese geochemists Tetsuya Torii and Joyo Ossaka. It was also reported from brine in Bristol Dry Lake , California, and stratified brine within blue holes in the Bahamas. It has also been noted within fluid inclusions bodies in the Bushveld complex. It occurs in association with halite and celestine
A similar mineral, sinjarite, the dihydrate of calcium chloride, crystallizes in the tetragonal Hydrophilite is a now discredited calcium chloride mineral that is considered to be either antarcticite or sinjarite.