The vermiculite is a natural Minéral of Chemical formula (Mg, Ca) _0,7 (Mg, Fe, Al) ₆ (Al, If) ₈O₂₂ (OH) ₄.8H₂O formed by the Hydratation of certain basaltic minerals, and often associated in nature with the Amiante. It has properties of expansion under the effect of heat (Exfoliation), and is mainly used commercially in exfoliée form. The vermiculite was extracted during the years 1960 with Libby in the Montana under Zonolite trade name (the Zonolite mark was acquired by W.R. Grace and Company in 1963). The operations of extraction on the site of Libby were stopped in 1990 following the problems due to asbestos. It is used in more than 35 million hearths to the the United States according to the US government.

In 2000, the worldwide production of vermiculite was of more than 500.000 tons, the principal producer countries being the China, the South Africa, the Australia, the Zimbabwe and the the United States.

Crystalline structure and physical properties

The vermiculite has a structure Argile uses Monoclinique of the 2:1 type, with two layers of the tetrahedral type for each layer of the octahedral type.

It has a capacity of expansion or average contraction and is regarded as a clay with low capacity of expansion. Its Dureté is from 1,5 to 2 and its Densité from 2,3 to 2,7. Its cation Capacité of exchange is raised, about 100-150 meq/100g. Clays of the vermiculite type have a structure of Mica S in which the Ion S K⁺ located between the layers were replaced by Cation S Mg²⁺ and Fe²⁺.

Commercial uses

• In moulded form, been dependant on Silicate of sodium for uses in:

• Thermo isolation at high temperature;
• refractory materials;
• fireproofing of structures in Steel or pipes;
• Substrates for the grounds of culture;
• Material of packing;
• Insulator of weak density;
• Additive for the fireproofing of Plaster S, mortars, Concrete S;
• Medium of growth for the Hydroponie.
• Support of growth for the micro-organisms to test the biodeterioration of the plastics

Exfoliée vermiculite manufacturers

The principal vermiculite world ore exporter is the South Africa, but much of industrialized countries industrialists exfoliateurs count on their ground. These industrialists usually also practice the exfoliation of the Perlite, the pearlite and vermiculite often being sold jointly. There exists an international organization The Vermiculite Association , who represents the interests of the industrialists of the field. Number of the members of this association are also adherent of The Perlite Institute .

Discusses concerning the health hazards

A article published on December 3rd, 2006 in the Salt Lake Tribune of Salt Lake City affirmed that the vermiculite and Zonolite contained asbestos and had led to the appearance of Cancer S in the same way as the latter. The article also affirmed that William Russell Grace and other industrialists had hidden the health hazards related to vermiculite and that several sites of the valley of Salt Lake City had been treated by the Agence of environmental protection of the United States because they presented a contamination by vermiculite. W.R. Thanks to denial vigorously these assertions.

See too

• Asbestos

• Pearlite
• Sepiolite