n. 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. [French (from perle, pearl, from Old French; see PEARL1) or German Perlit (from Perle, pearl, ultimately from Vulgar Latin *pernula).] per·litic (pər-lĭtĭk) adj. |
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