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Vermiculite: Background & Uses

ver·mic·u·lite (v ər-mĭk’y ə-līt’) . n. Any of a group of micaceous hydrated silicate minerals related to the chlorites and used in heat-expanded form as insulation and as a planting medium. (from www.dictionary.com)

Vermiculite is the mineralogical name given to hydrated laminar magnesium-aluminum-iron silicate and is a naturally occurring mineral composed of shiny flakes, resembling mica. Vermiculite is found in various parts of the world. Locations of the large commercial mines include Australia, Brazil, China, Kenya, South Africa, Zimbabwe and the United States.

Vermiculite is mined through a surface operation where the ore is separated from other minerals, and then classified into several basic particle sizes. When vermiculite is heated to a high temperature, the flakes expand as much as eight to 30 times their original size, resulting in a lightweight, fire-resistant, and odorless material. When subjected to heat vermiculite expands into worm-like pieces, thus the name, derived from the Latin ‘vermiculare’ – to breed worms.

The expansion process, or exfoliation, is routinely accomplished in commercial furnaces designed specifically for this purpose. Vermiculite is most commonly used in its exfoliated (expanded) form, although vermiculite is also found in finely ground and liquid dispersion forms. The ground and liquid forms utilize vermiculite’s high aspect ratio platelets to produce unique end-use applications.

Vermiculite has been used in many industries for over 80 years, and it is primarily used in the construction, agricultural, and industrial markets. Vermiculite’s many uses include:

  • High-temperature, refractory and loose-fill insulation;
  • Fireproofing of structural steel and pipes;
  • Growing media and soil conditioner for fruits, vegetables, and flowers;
  • Packing material;
  • Lightweight concrete to improve insulation and increase noise absorption;
  • As an additive to fireproof wallboard;
  • A means to permit slow cooling of hot pieces in glassblowing, lampwork, and steelwork;
  • Use in in-ground swimming pools to provide a smooth pool base;
  • Absorbing hazardous liquids for solid waste disposal;
  • Use in gas fireplaces to simulate embers;
  • Bio-remediation aid to clean contaminated soils and sites.

In its pure form, vermiculite is one of the safest, most versatile minerals in the world. Except for the mines in Montana, where the asbestos exposure was known to be very high, no asbestos-related diseases have been found among the workers in any of the other vermiculite mines.

When vermiculite is used and handled according to suppliers’ recommendations, it can be environmentally safe. As with all other materials and their derivatives, professionals and consumers alike should follow and comply with local and national regulatory requirements when handling the mineral. Local agencies should be contacted regarding specific requirements for handling vermiculite and vermiculate products.

Asbestos Connection

Vermiculite ores often contain a range of other minerals including, in some cases, asbestos. Asbestos is not a major contaminant, and only a few ore deposits have been found to contain more than trace amounts of asbestos minerals. Unfortunately, the largest vermiculite mine in the United States, the Libby, Montana mine, was found to have heavy asbestos contamination.

Asbestos is a known carcinogen and is proven to cause mesothelioma, a serious cancer caused by breathing in the asbestos fibers that then become lodged in the thin membrane that lines and encases the lungs.  Often called “asbestos cancer,” the cancer is highly aggressive and is resistant to many treatment options. A diagnosis is not often made until symptoms appear.  At this time the prognosis is usually grim with no known cures, and with the average survival time varying from 4 – 18 months after diagnosis.

The former vermiculite mine in Libby was found to have tremolite asbestos as well as winchite and richterite (both fibrous amphiboles). Pure vermiculite does not contain asbestos and is non-toxic, but it can become contaminated if there is a presence of a secondary mineral called diopside in and around the vermiculite deposits. Basically, after millions of years of weatherization, the biotite turns into vermiculite and the diopside turns into asbestos. This results in the commingling of the minerals.

Because of the high concentrations of asbestos found at Libby, and the resulting health issues, all vermiculite mines have been tested, and continue to be tested, for asbestos levels. There seems to be convincing evidence that the asbestos concentrations were unique to Libby.

At all of the mines currently supplying vermiculite to processing companies in North America, Europe and elsewhere throughout the world, testing is required. To date, asbestos in those materials has either not been found or detected, or only trace amounts below current regulatory limits have been detected. They all comply with current EPA, OSHA, and international regulatory requirements. One exception is the Virginia Vermiculite mine in Louisa, Virginia, which has been found to contain high levels of asbestos.

Asbestos Exposure Risks

Asbestos fibers may be released into the air by the disturbance of asbestos-containing material during product use, demolition work or mining operations. Exposure may occur only when the asbestos-containing material is airborne. When asbestos becomes airborne, the fibers can be inhaled into the lungs, where they can cause significant health problems with varying symptoms.

Continued exposure can increase the amount of fibers that remain in the lungs. Asbestos fibers lodged in lung tissue over time may cause serious lung diseases including, asbestosis, lung cancer or mesothelioma. If there is a concern about possible exposure, consult with a physician who specializes in lung diseases, also known as a pulmonologist.


United States EPA
The Vermiculite Association

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