Lithium Ores

natural mineral formations with a lithium content sufficiently high to make the extraction of lithium or lithium compounds economically profitable. Lithium usually occurs in ores in the form of characteristic minerals; a small quantity of lithium is a component of rock-forming minerals (micas, tourmalines, and others) as an isomorphic impurity. Lithium is also extracted from the natural brine of certain lakes and mineralized waters. The principal lithium-containing minerals of industrial value are spodumene, LiAl[Si₂O₆], which contains 6—7 percent Li₂O; petalite, LiAl[Si₄O₁₀], containing 3.5–4.9 percent Li₂O; and amblygonite, LiAl[PO₄](F,OH), containing 8–10 percent Li₂O; as well as lithia micas, such as zinnwaldite, K(Fe,Mg) LiAl[Si₃AlO₁₀](OH,F)₂ containing 3.0–3.5 percent Li₂O, and lepidolite, KLi_1.5 Al_1.5[SI₃AlO₁₀](F,OH)₂, containing 4–6 percent Li₂O. In specific cases, lithium-containing minerals form large deposits of lithium—for example, spodumene crystals sometimes reach a length of 2–10 m.

High concentrations of lithium are observed primarily in endogenic deposits and are associated with granitic magmas. Lithium ores are formed during postmagmatic processes at relatively high temperatures (250°-500°C) and at depths of the order of 1.5–7.0 km. The following industrial types of lithium ore deposits are distinguished:

(1) Sodium-lithium rare-metal pegmatite deposits (according to the classification method of A. E. Fersman), which includes the following, subtypes: spodumene pegmatites (the main type of lithium ore deposit), lepidolite-spodumene pegmatites (0.6–1.2 percent Li₂O), and lepidolite-petalite pegmatites.

(2) Lithium fluoride rare-metal granite deposits (0.2–0.3 percent Li₂O).

(3) Zinnwaldite or lepidolite greisens in association with zinn-waldite-containing cassiterite-tungsten quartz veins (of small industrial value).

Lithium ores are usually dressed by the flotation method or are separated out in heavy suspensions. Spodumene ores can also be dressed by roasting up to 1000°C, at which point the naturally occurring α-spodumene is converted into another polymorphous variety (β -spodumene). The conversion is related to a marked increase in volume, which causes the ore to crack, readily converting the spodumene into a powder. Sulfuric acid is used to dissociate β-spodumene. All lithium ore deposits are complex in character. In addition to lithium, spodumene and petalite ores also contain beryllium, tantalum, cesium, rubidium, and tin. Feldspar, which invariably occurs in ores, may be used as a raw material in the production of ceramics. Zinnwaldite lithium ores usually contain tin and tungsten. The largest known lithium ore deposits are found in Canada, the USA, Southern Rhodesia, South West Africa, Brazil, and the USSR.