Vermiculite

VERMICULITE (from the Latin word "vermiculus", which means "small worm" - * EN: vermiculite; DE: Vermiculit; FR: vermiculite; ES: vermiculita; RU: вермикулит) is the mineral of the class of silicates, of the group of the trioctahedral hydromicas.

The chemical composition is variable (%): MgO - 14-25; FeO - 1-3; Fe2O3 - 3-17; Al2O3 - 10-17; SiO2 - 34-42; H2O - 8-15. The varieties are the nickel vermiculite, and the cupriferous vermiculite. There are also known these admixtures: titanium, nickel, zinc, copper, sodium, and potassium. Vermiculite crystallizes itself into the monoclinic crystal system. Within the interlayer gaps, there are located the exchangeable cations (most often magnesium and calcium), and the molecules of water. The crystals are tabular, often pseudohexagonal, with the cleavage along the (001) plane. There are also characteristic the aggregates with the small and large flakes. The colour is bronze-yellow, golden-brown, brown-green. The hardness is 1-1.5. The density is 2400-2700 kilograms per cubic metre. During the rapid heating, vermiculite swells, the volume is increasing by 20-30 times, and, during this process, the density becomes 100-150 kilograms per cubic metre and less. After the annealing, there is obtained the lightweight material with the great heat and sound insulating properties. For vermiculite, there is characteristic the ability for the inter-cationic exchange; the magnesium between the layers is easily replaced with calcium, barium, lead, lithium, cesium, and ammonium. Vermiculite is formed within the weathering crusts on the surface of the phlogopite-containing and biotite-containing rocks. The typical fatherland deposit with vermiculite is the Kovdorskoe deposit on the Kola peninsula; there are also known the deposits at the Urals mountains, within Siberia, and within Ukraine (Volyn); abroad, there are known the deposits within the USA (the South Carolina state, and the Montana state), Republic of South Africa (the Phalaborwa deposit), Argentina, Brazil, India, Japan, Tanzania, West of Australia, Canada, Chile, Mexico, Malawi, and other places.

The explored reserves of vermiculite within the industrially developed capitalist and developing countries are approximately 180 million tonnes, including 90 million tonnes within the USA, and 73 million tonnes within the Republic of South Africa (1980). The extraction within the capitalistic countries is approximately 560 thousand tonnes, of which 300 thousand tonnes is within the USA, and 210 thousand tonnes is within the Republic of South Africa (1978). The vermiculite, which has been roasted after the stage of swelling, is used as the lightweight filler for concrete, for the production of the fire-resistant heat-protecting and sound-protecting materials, and of the heat-preserving materials. Within the metallurgy, vermiculite is used for the heat-insulation of the furnaces, and for the heat-protection of the metal. Vermiculite is also used within the outer space machinery, within the aircraft engineering, within the transport construction, within the production of the anti-fri ction materials, rubber, plastics, paints, poisonous chemicals, and so on. Vermiculite is beneficiated using the gravity and flotation methods. The collectors are the strongly alcaline amines, and the petroleum oils; the regulator for the environment is the sulfuric acid; the activators are Al2(SO4)3, and Pb(NO3)2; the depressors are the starch, glues, and tannic acid.