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The Mineral cryolite

Cryolite with Siderite

Cryolite is an unusual mineral with an interesting history. It was commercially mined in large quantities in Greenland since the mid-1800's, and this one locality produced almost the entire source of collectors specimen. Cryolite's economic importance was as a flux for the production of aluminum, but its significance became entirely diminished once it was able to be synthesized. This made the mining operation no longer necessary, and mining and production of Cryolite was entirely stopped.

Cryolite is usually lightly colored, and it commonly associated with contrasting dark brownish yellow Siderite. The Siderite may also be in microcrystals covering the Cryolite, making it appear yellow or brown. Cryolite has a very low refractive index, similar to water, and therefor if transparent pieces put in water, they will blend right in and be hard to distinguish in the water.

Crylolite is name afte the Greek words kryos - Ice, and lithos - stone, based on the typical icy-white color of this mineral.

Chemical Formula

Na₃AlF₆

Color

White, colorless, light yellow, light tan, brown

Crystal System

Monoclinic

Properties

Streak
White

Hardness
2.5

Transparency
Transparent to translucent

Specific Gravity
2.9 - 3.0

Luster
Vitreous, pearly

Cleavage
None, though exhibits good parting

Fracture
Uneven

Tenacity
Brittle

Other ID Marks
1) Has a weak salty taste.

2) Slightly soluble in water.

3) May fluoresce bluish-white.

Crystal Habits

Individual crystals, which are rare, are usually prismatic. Most often roughly crystallized with multiple pseudocubic or pseudo-octahedral faces appearing similar to cleavages. Also massive and grainy.

3D Crystal Atlas

Additional Information

Composition
Sodium aluminum fluoride

In Group
Halides

Striking Features
Mode of occurrence and taste.

Environment
Granite pegmatites.

Rock Type
Igneous, Metamorphic

Uses

Cryolite has been mined for its use as a flux to dissolve Bauxite in the recovery of aluminum by way of the Hall–Héroult process. It was eventually synthesized and is no longer mine economically.

Noteworthy Localities

The most important mine was at Ivittutt (Ivigtut), Arsuk, Greenland, where Cryolite was extensively mined for its use as a flux in the production of aluminum. This was the world's only mine exclusively for Cryolite, and has been its only major producer. Upon the synthesizing of Cryolite, mining at this location was no longer economical, and the mine permanently closed in 1987. The town was abandoned shortly thereafter.

Cryolite has also been mined in St. Peters Dome, Cheyenne District, El Paso Co., Colorado; and small amounts have come from the Morefield Mine, Winterham, Amelia Co., Virginia. In Canada, small Cryolite crystals have come from Quebec at the Poudrette Quarry, Mont St. Hilaire; and the Francon Quarry, Montreal.