perlite
UK[ˈpɜːlaɪt]US[ˈpɜːrlaɪt]
n
a light, porous, glassy volcanic rock, typically formed by the hydration of obsidian, used especially in horticulture for improving soil aeration and drainage.
Etymology
the word 'perlite' entered english in the early 19th century as a direct borrowing from the french mineralogical term 'perlite'. the french name was inspired by the visual resemblance of the rock's characteristic concentric, cracking pattern to the iridescent layers of a pearl, from the old french 'perle'. the ultimate origin of 'pearl' is likely latin 'perna', meaning 'leg' (referring to a ham-shaped bivalve) or possibly a pre-latin mediterranean substrate word. the term's logic is purely descriptive, linking the material's lustrous, fractured appearance to a familiar natural object, with no deeper morphemic segmentation in its modern english form.
Analysis
this is a simplex word. it is a modern mineralogical term derived directly from the french word 'perlite', which itself is based on the french 'perle' meaning 'pearl'.
Examples
the gardener mixed perlite into the potting soil to prevent it from becoming too compact.
due to its excellent insulating properties, expanded perlite is often used in construction materials.
the volcanic glass obsidian can alter into perlite through a process of hydration.