Definitions for vermiculitevərˈmɪk yəˌlaɪt
Random House Webster's College Dictionary
any of a group of platy minerals, hydrous silicates of aluminum, magnesium, and iron, that expand markedly on being heated: used for insulation and as a plant growth medium.
Origin of vermiculite:
1815–25, Amer.; vermicul (ar ) + -ite1
A hydrated silicate mineral which expands on heating; it is used in insulation and as a medium for planting
Origin: vermiculus, wormlet for its fibrous nature and tendency to expand into worm-like shapes when heated
a group of minerals having, a micaceous structure. They are hydrous silicates, derived generally from the alteration of some kind of mica. So called because the scales, when heated, open out into wormlike forms