|a white or colourless glassy variety of orthoclase in the form of prismatic crystals. It occurs in metamorphic rocks and is a minor gemstone. Formula: KAlSi3O8|
|[C18: via Italian from French adulaire, after Adula, a group of mountains in Switzerland]|
a feldspar mineral and potassium aluminosilicate (KAlSi3O8). It commonly forms colourless, glassy, prismatic, twinned crystals in low-temperature veins of felsic plutonic rocks and in cavities in crystalline schists. Typical occurrences include the schists of the Alps. Some adularia show an opalescent play of colours and are called moonstone.
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