perlIte

[Ger.perl=pearl; suff. -ite ( Petrol.).] Petrol.: A variety of obsidian (q. v.) with an enamel-like luster and a gray color. Structure, usually granular, fine to coarse-grained, occasionally spherulitic. Sub-translucent to opaque. Under the microscope it exhibits numerous more or le elliptical or spheroidal cracks, which are due to the contraction of the rock while cooling. chin, bench; go, gem; thin, this; II. Bot . The same as PERSISTENT (q. v.). Used chiefly of leaves.