Vermiculite is a mica-like mineral that is mined and milled into various sized grade ore. The ore is exfoliated (expanded by being heated and popped, much like popcorn) to produce a lightweight product that is used in agriculture, building products, horticulture, and in places where insulation is needed. The expanded vermiculite looks like small pellets, which are layered like an accordion. It is usually gold-brown or metallic in color.
Much of the vermiculite used in the United States originated from a mine in Libby, Montana that was owned by W. R. Grace & Co., formerly the Zonolite Company. This vermiculite mine was contaminated with varying amounts of fibrous amphiboleasbestos. One of the products produced from Libby, MT vermiculite was Zonolite Attic Insulation (ZAI). ZAI was manufactured and sold throughout the United States and Canada from approximately 1925 to 1984. The Libby vermiculite mine was closed in 1990. Older versions of this insulation are called "Zonolite Unifil", "Zonolite Eco-fill", and "Zonolite Insulating Fill". The vermiculite sold today does not come from the Libby MT vermiculite mine. If you suspect you have vermiculite insulation in your home DO NOT DISTURB IT. Any disturbance is likely to release asbestos fibers into the air. The EPA and ATSDR strongly recommend:
- Vermiculite insulation be left undisturbed in your attic. It is best to assume that the material may contain asbestos for safety's sake.
- Do not store boxes or other items that when retrieving material would disturb the insulation.
- Children should not be allowed to play in an attic that has vermiculite insulation.
- Hire professionals trained and certified to handle asbestos to safely remove the material if you plan to remodel or renovate.
- Never attempt to remove the insulation yourself.
