vermiculite

[ ver-mik-yuh-lahyt ]
/ vərˈmɪk yəˌlaɪt /

noun

any of a group of platy minerals, hydrous silicates of aluminum, magnesium, and iron, that expand markedly on being heated: used in the expanded state for heat insulation and as a plant growth medium.

Origin of vermiculite

An Americanism dating back to 1815–25; vermicul(ar) + -ite1

British Dictionary definitions for vermiculite

vermiculite
/ (vɜːˈmɪkjʊˌlaɪt) /

noun

any of a group of micaceous minerals consisting mainly of hydrated silicate of magnesium, aluminium, and iron: on heating they expand and exfoliate and in this form are used in heat and sound insulation, fireproofing, and as a bedding medium for young plants

Word Origin for vermiculite

C19: from vermicul ( ar) + -ite 1