Is Vermiculite as Dangerous as Asbestos?

Date Posted: December 14, 2011

Pure vermiculite is harmless and used for insulation, fireproofing and acoustics. A very versatile mineral, it’s also used in gardening as an alternative to soil when it’s mixed with compost. It’s also used to protect bulbs and root crops, incubate eggs, grow mushrooms and for many other purposes. The problem is that when vermiculite is mined it sometimes contains asbestos.

Pure vermiculite is made of plates of green or golden yellow to brown crystals. It’s slightly acid soluble, but when it’s heated to about 572 degrees Fahrenheit it loses water, flakes and expands from 18 to 25 times its original volume. It also erupts into long, twisted, wormlike shapes that give it its name, which means “to breed worms.” As it grows, vermiculite’s density decreases until it can float on water. Because of this lightness when it’s heated, vermiculite is sought after for insulation, as well as paper, paint and plastics. There are large concentrations of vermiculite found in South Africa; Milbury, Massachusetts; Libby, Montana; Macon, North Carolina; Argentina; Western Australia and Canada. Much of the vermiculite was contaminated with asbestos.