in natural history, a class of fossils, not inflammable nor soluble in water; when pure, it is pellucid and colourless, and emulating the appearance of crystal, but wanting its distinguishing characters; composed of plane and equable plates, not flexible nor elastic, not giving fire with steel, readily calcining in a small fire, and fermenting violently with acids, and wholly soluble in them.

The spars, in general, are found in the fissures of stones, and about mines. Derbyshire affords enough of them to supply the whole world; and the German mines afford yet larger quantities.