[pur-lahyt] 
| a volcanic glass in which concentric fractures impart a distinctive structure resembling masses of small spheroids, used as a plant growth medium. |
| per·lite also pearl·ite (pûr'līt') 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 Perlite (from Perle, pearl, ultimately from Vulgar Latin *pernula).] per·lit'ic (pər-lĭt'ĭk) adj. |
laɪt