lepidolite

Before spodumene became the sole ore for the recovery of lithium for chemical use, lepidolite was used as a lithium source.
One process for recovery of lithium from lepidolite used sulfuric acid in a procedure similar to that used by the Lithium Corporation of America for spodumene. A more recent method involved heating a mixture of lepidolite and potassium sulfate to just below the melting point and extracting the mixture with water to recover a solution of lithium sulfate.

Lepidolite is named after the Greek word Lepidos, which means "scale". This is due to the typical formation of the mineral in scale-like clusters. Lepidolite contains between 1.23% to 5.90% lithium oxide and has a monoclinic crystal system with dimensions a=5.3, b=9.2, c=10.2, and β=100°. The crystal symmetry is m or 2/m, with pseudo-hexagonal plates forming fine scale-like clusters. Its attractive light purple color is combined with a glass luster, a hardness of 2-3, and a relative density of 2.8-2.9. There are over 150 minerals containing lithium, but only 30 of these are independent lithium minerals. The most important of these minerals is spodumene, followed by lepidolite.

Lepidolite, a variety of mica, is a fluorosilicate of potassium, lithium and aluminum found in pegmatites. Generally, rubidium occurs as an impurity.