Vermiculite Identification & History

Closeup of Libby VermiculiteVermiculite is easy to identify if you know what to look for. On this page are several pictures of what is now called "Libby Vermiculite" by the EPA. Take note of the appearance of the "rocks" and alert the EPA if you find anything resembling these images on your property.
The asbestos found in vermiculite materials from the former Zonolite Mine (Libby amphibole asbestos) in Libby is fairly unique. Asbestos is known to cause health effects at low levels of exposure. Because of this, the EPA recommends that people avoid all contact with vermiculite materials from Libby.

Asbestos Warning Label

Vermiculite Basics

Vermiculite is a hydrous, silicate mineral that is classified as a phyllosilicate and that expands greatly when heated. Exfoliation occurs when the mineral is heated sufficiently, and the effect is routinely produced in commercial furnaces. Vermiculite is formed by weathering or hydrothermal alteration of biotite or phlogopite. Large commercial vermiculite mines currently exist in Russia, South Africa, China, and Brazil.

Large Vermiculite Rock

Vermiculite Risks

Although not all vermiculite contains asbestos, some products were made with vermiculite that contained asbestos until the early 1990s. Vermiculite mines throughout the world are now regularly tested for it and are supposed to sell products that contain no asbestos. The former vermiculite mine in Libby, Montana, did have tremolite asbestos as well as winchite and richterite (both fibrous amphiboles) — in fact, it was formed underground through essentially the same geologic processes as the contaminants. A vermiculite mine in Virginia has also been found to be contaminated by asbestos.

Large Vermiculite Rock

Libby Vermiculite

The largest and oldest vermiculite mine in the United States was started in the 1920s, at Libby, Montana, and the vermiculite was sold under the commercial name Zonolite. The Zonolite brand and the mine was acquired by the W.R. Grace Company in 1963. Mining operations at the Libby site stopped in 1990 in response to asbestos contamination. While in operation, the Libby mine may have produced 80% of the world's supply of vermiculite.

Libby, MT vermiculite newspaper clipping

Vermiculite & Asbestos

After a 1999 Seattle Post-Intelligencer story claimed that asbestos-related disease was common in the town, the EPA, in response to political pressure, made cleanup of the site a priority and called Libby the worst case of community-wide exposure to a toxic substance in U.S. history. To date, approximately 1,200 residents of the Libby area have been identified as suffering from some kind of asbestos-related abnormality. On June 17, 2009, the EPA issued a public health emergency in and near Libby, thereby allowing federal agencies to provide funding for health care, and for removal of contaminated insulation from affected homes.


Libby Vermiculite If you have found any "rocks" that resemble these pictures, then you may have found Vermiculite on your property. Please call (406) 293-6194 to talk to a Libby EPA specialist.