Vermiculite is a natural mineral which expands with the application of heat. It is formed by hydration of certain basaltic minerals, and is often found in association with asbestos. Mining operations in Libby, Montana were closed in 1990 in response to asbestos contamination. Expanded vermiculite is used as a soil conditioner, as loose-fill insulating and packing material, as an insulating filler for plaster and concrete compounds, and as a carrier for dry handling and slow release of agricultural chemicals.
World production of vermiculite in the year 2000 exceeded 500 kilotons (metric). Major producers of vermiculite include China, South Africa, Australia, Zimbabwe, and the United States of America.
Vermiculite is often used along with perlite as a soil additive for potted plants, and as growing mediums for hydroponics.