Vermiculite

Vermiculite is the geological name given to a group of hydrated laminar minerals that are aluminium iron magnesium silicates, a hydrous phyllosilicate mineral. Although vermiculite is often listed as a Deleterious material because of its connection to asbestos, pure vermiculite does not contain asbestos and is non-toxic. Impure vermiculite may contain, apart from asbestos, minor diopside or remnants of precursor minerals biotite or phlogopite, most mines are tested for the presence of asbestos.

Most vermiculite used in industry is exfoliated vermiculite, that is heated to a high temperature a separation of the layers of the material at micro level. This heating exfoliation process causes the vermiculite to expands to up to 12 times its original volume, converting the dense flakes of ore into lightweight porous granules which contain innumerable air layers. These air pockets make the material lightweight, with good water absorption, heat retention and fireproofing qualities.

Until the 1990's various products were made with vermiculite and asbestos, such as for example home insulation, where some amount of asbestos was added to assist with structure and fireproofing. Today, due to significant health risks vermiculite asbestos products are rare, however products containing just vermiculite continued to be used in construction as well as gardening, filtration and construction.

Vermiculite is used in the car industry for brake pads, in water treatment, seed germination and soil treatment, and in fireproof coatings. In construction it continues to be used in lightweight concrete roof structures and screed floors, as an aggregate in renders and insulating plasters, as fireproof wall boards and as loose fill cavity insulation.

The global reserves of perlite are estimated to be around 2.36 million tonnes, with around 500,00 tonnes produced each year primarily from South Africa, the US, Brazil, and Russia. Perlite is a very similar material to vermiculite with similar uses but some slightly different characteristics.

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• Phase change materials.
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