Editorial Feature

Antarcticite - Occurrence, Properties, and Distribution

May 12 2014

Antarcticite was named after its place of first occurrence – Antarctica. It is an uncommon calcium chloride hexahydrate mineral.

Properties of Antarcticite

The following are the key properties of antarcticite:

Cell Data
- Space group: P321
- a = 7.89–7.907
- c = 3.95
- Z = 1

Crystal Data
- Hexagonal
- As aggregates of acicular crystals, to 15cm, with poor terminations
- X-ray powder pattern: 3.44 (24), 2.80 (23), 2.16 (23), 2.60 (22), 3.98 (18), 2.28 (13), 6.92 (9)

Chemical Composition

Elements	Content 1	Content 2	Content 3
H₂O⁺	49.2	49.27	49.34
Cl	32.7	33.14	32.37
Ca	17.5	17.25	18.29
Na	0.34	0.30	-
Mg	0.41	0.015	-
K	0.008	-	-
Si	-	0.003	-
Fe	-	0.003
Al	-	0.002	-
Total	100.1	99.98	100.00

Optical Properties
- Optical class: Uniaxial (–)
- ω = 1.550
- ε = 1.490–1.500

Estimated Properties

Electron density	Bulk density (electron density) = 1.78 g/cm³ note: Specific gravity of antarcticite = 1.71g/cm³
Photoelectric	PE_Antarcticite = 4.31 barns/electron U=PE_Antarcticite x ρ electron density= 7.67 barns/cm³
Fermion index	Fermion index = 0.00046 Boson index = 0.99953
Radioactivity	Antarcticite is not radioactive

How to Identify Antarcticite

Antarcticite can be identified in the field by its colorless structure. Its transparent form has {0001} perfect, {1010} very good cleavage. This mineral has a vitreous luster, with white streak. The fracture on this mineral is brittle.

The density of antarcticite is 1.705 - 1.725 g/cm³, with a hardness of 2-3 - between gypsum and calcite.

Global Distribution

Antarcticite is distributed in the following places:

USA - At Bristol Dry Lake, San Bernardino Co. California
Bahamas - On North Andros Island
Antarctica - From Don Juan Pond, Wright Valley, and elsewhere around Mt. Erebus, Victoria Land
South Africa - From the Bushveld complex, on Driekop Farm, Transvaal

Occurrence of Antarcticite and Useful Mineral Association

Antarcticite occurs in a precipitate from highly saline brines under very arid conditions, and in stratified fresh to brackish salt water columns in onshore blue holes. It is also an abundant component of inclusions in quartz in a zoned mafic pegmatoid. It is often associated with minerals such as halite, gypsum, and celestine.