- Geol. a greenish volcanic glass, similar to obsidian, with a pearly luster and multiple, minute concentric cracks, used as insulation and in making concrete, plaster, etc.
Origin of perliteFrench from perle, pearl
A natural volcanic glass similar to obsidian but having distinctive concentric cracks and a relatively high water content. In a fluffy heat-expanded form perlite is used as a lightweight aggregate, in fire-resistant insulation, and in soil for potted plants.
Origin of perliteFrench ( from perle pearl ) ( from Old French; see pearl 1. ) or German Perlit ( from Perle pearl ) ( ultimately from Vulgar Latin pernula )
From French perle (“pearl") + -ite