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
C19: from vermicul(ar) + -ite1
vermiculite in American English
(vərˈmɪkjəˌlaɪt)
US
noun
any of a number of very soft, monoclinic, hydrous silicate minerals resulting usually from alterations of mica and occurring in tiny, leafy scales that expand greatly when heated: used for insulation, water adsorption, etc.