Vermiculite is a layered structure of magnesium aluminum silicate water secondary metamorphic minerals, like mica ore outside, usually black (K) mica by hydrothermal alteration or weathering from, because heat dehydration deflection when the expansion was like, shape resembles a leech, it said vermiculite. 
 The chemical formula of vermiculite (Mg, Ca) 0.7 (Mg, Fe, Al) 6.0 [(Al, Si) 8.0] (OH4.8H2O) 
 Divided by stage of vermiculite vermiculite and expanded vermiculite ore, can be divided by color golden vermiculite, vermiculite silver, white vermiculite. 
 Vermiculite ore roasting at high temperatures the rapid expansion of its volume can be 8-20 times the proportion after expansion 130-180kg/m3, has a strong thermal insulation properties.