- 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 pearl1) or German Perlit (from Perle, pearl, ultimately from Vulgar Latin *pernula).