Vermiculite is a hydrated magnesium-aluminum-iron silicate Flakes of raw vermiculite concentrate are mica-like in appearance and contain water molecules within their internal structure. When the flakes are heated rapidly at a temperature of 900 degree celsius or higher, the water flashes into steam, and the flakes expand into accordion-like particles. The color, which can range from black and various shades of brown to yellow for the raw flakes, changes to gold or bronze. This expansion process is called exfoliation, and the resulting lightweight material is chemically inert, fire resistant, and odorless. In lightweight plaster and concrete, vermiculite provides good thermal insulation. Vermiculite can absorb such liquids as fertilizers, herbicides, and insecticides, which can then be transported as free-flowing solids.

China Vermiculite.—Although data were not fully available, output of vermiculite was estimated to be at least 30,000 to 40,000 t/y (2003) from the four main producers in Xinjiang Province. An additional 15,000 t of output was estimated to have been produced in Hebei Province. Hebei Vermiculite classifies into two types. Silver-white vermiculite contains 5% to 13% iron oxide (Fe₂o₃) and is for use in the construction industry. Golden yellow vermiculite, with 16% to 22% Fe₂o₃, is used in agriculture and horticulture. Export destinations for Chinese vermiculite included Japan, the Republic of Korea, and North America