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Spodumene
Spodumene is a lithium aluminum silicate (8.0% Li2O, 27.4% Al2O3, 64.6%SiO2) and is the world's most common commercially mined lithium ore mineral. Petalite, lepidolite and amblygonite are also mined in different parts of the world. Spodumene is a pegmatite mineral that has a glassy lustre and may be opaque; it is nearly white in the low-iron variety and dark green in iron-rich crystals. The transparent variety can be colourless, pink, yellow or green. Good quality clear crystals are used as gems. These include lilac-pink kunzite, coloured by manganese, and yellowish-green or emerald green hiddenite, coloured by chromium and iron.
Spodumene ore and concentrate are used mainly in the glass, ceramic and porcelain enamel industries. Commercial spodumene ore concentrates contain between 5% and 7.5% lithia (Li2O). Lithia as spodumene is used in the glass and ceramic industries to decrease viscosity, improve the forming properties, increase thermal shock resistance (pyroceramics), reduce flux consumption and firing temperature, and improve the stability of glass exposed to radiation such as in TV faceplate glass.
Spodumene competes with natural brines as a source of lithium in the production of lithium carbonate, which is used in aluminum reduction cells to improve the conductivity of the molten bath. The pharmaceutical high-purity grade of lithium carbonate is used in the treatment of manic-depressive psychosis. Above all, lithium carbonate is used as a feedstock for the production of lithium chemicals such as lithium hydroxide, lithium chloride, lithium nitride and lithium metal.
The production of lithium carbonate from spodumene is much more energy intensive than the production from lithium chloride-enriched brines. Spodumene concentrate must be heated to about 1100°C to make it more reactive. Then it is finely ground, mixed with hot sulphuric acid and heated to 250°C to form lithium sulphate. Water is added to dissolve the lithium sulphate. Finally, lithium sulphate is treated with soda ash to yield lithium carbonate. Lithium chloride-enriched brines that contain somewhere around 300 parts per million (ppm) only need to be pumped from the ground and deposited in evaporation ponds where the natural evaporation process increases the concentration to 6000 ppm in a period of 1-2 years. The liquid is then pumped to a processing plant where it is reacted with soda ash, precipitating lithium carbonate.
In Canada, Tantalum Mining Corporation (Tanco), operated by Cabot Specialty Fluids, a subsidiary of Cabot Corporation of Boston, extracts spodumene, tantalum and pollucite from a pegmatite mine near Lac-du-Bonnet, Manitoba. Tanco produces a total of 16 000 t to 24 000 t per year of spodumene products concentrates including standard-grade spodumene, Spodulight and Montebrasite (a "commercial lithium mineral product").