Vermiculite History
From about 1920 to 1990 vermiculite was mined in Libby, Montana. During that time, the Libby mine produced most of the world's supply of vermiculite. Some of the products that vermiculite was used for include fertilizer, building insulation, and potting soil.
The mine was closed in 1990 after tests confirmed that the vermiculite found at the Libby mine contained a type of asbestos element. Termolite-actinolite is a naturally occurring asbestos fiber.
If you are concerned that you are using a vermiculite product containing asbestos, contact the manufacturer for details, or you can take it to a lab for testing.