SPAR, in natural history, a class of fossils not inflammable nor soluble in water: when pure, it is pellucid, and colourless; emulating the appearance of crystal, but wanting its distinguishing characteristics; composed of plane and equable plates; not flexible nor elastic; not giving fire with steel; readily calcining in a small fire; fermenting violently with acids, and totally soluble in them.—The spars in general are found in the fissures of stones, and about mines. Vast quantities are found in the German mines, and in those of Derbyshire in England.