Be safe when exposed to vermiculite. The source of over 70 percent of all vermiculite sold in the United States from 1919 to 1990 is from a mine near Libby, Montana. There is a large deposit of asbestos in the vermiculite there. The MAJORITY of vermiculite insulation used in the United States under the brand name Zonolite was Vermiculite from Libby. Vermiculite insulation in your home, therefore, is likely contaminated with asbestos. Take the necessary steps to protect yourself and your family from exposure to asbestos.
This according to the EPA website.