Antarcticite

• IMA 1965-015

Antarcticite (also Antarkticit ) is a very rare occurring mineral from the mineral class of halides. It crystallizes in the trigonal crystal system with the chemical composition of CaCl 2 • 6H 2 O, is thus seen chemically a hydrous calcium chloride. The mineral forms aggregates of colorless acicular crystals up to 15 cm.

Special Features

The mineral is very hygroscopic and readily dissolves in water.

Etymology and history

The mineral was first found on December 30, 1963 by Tetsuri Torii in the type locality, the Don Juan Lake, a 100 × 300 -meter, but only 10 cm deep, highly saline lake in Wright Valley in Victoria Land ( Antarctica ). It was named after the continent of Antarctica, where the type locality is named.

Classification

In the classification by Strunz Antarcticite is counted to the simple halides. After the 8th edition, it forms a group together with bishofite, Eriochalcit, hydrohalite, Nickelbischofit, Rokühnit and Sinjarit. The 9th edition, it forms a separate sub-group of simple water-containing halides with a ratio of metal halide to 1:2.

In the classification by Dana, it forms a separate subgroup of the crystal- water-free and -containing halides with a ratio of metal to halide of 1:2.

Education and Locations

Antarcticite crystallizes only under very dry conditions from highly saline solutions. According to the composition of the mineral, especially a high calcium and chloride content is important. Thus the water of the Don Juan lake is very salty so that this does not freeze in the Antarctic winter. Furthermore, the mineral in the transition from salt to fresh water can occur in the Blue Hole and as an inclusion in quartz in mafic pegmatites. Crystallized Antarcticite of highly saline water from, it is associated with halite, gypsum and celestite.

From the very rare mineral only a few localities are known. In addition to the type locality was found Antarcticite only in the Mary Kathleen mine in Mount Isa (Australia), belonging to the Bahamas island of North Andros, Preissac in the Canadian province of Quebec, Zheleznogorsk - Ilimski in Russia, Driekop Mine in the Bushveld complex ( South Africa) and the Bristol Lake, a salt flat in the U.S. state of California.

Crystal structure

Antarcticite crystallizes in the trigonal crystal system in the space group P321 with lattice parameters a = 7.89 Å and c = 3.95 Å, and one formula unit per unit cell.