Vermiculite
[vә:'mikjulait]
Definition
(noun.) any of a group of yellow or brown hydrous silicate minerals having a micaceous structure.
Checked by Jerome--From WordNet
Definition
(n.) 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.
Checker: Reginald