**Bulk pricing available** Vermiculite is a naturally occurring mineral compound that expands when heated. A member of the phyllosilicate group of minerals, it resembles mica in appearance. In its pure form, vermiculite is clean, odorless, nontoxic and sterile. Vermiculite helps to aerate soil while simultaneously retaining water and nutrients, which it then releases over time. Vermiculite is therefore useful in seed sowing and propagation. It can also be added to house plant compost.