The mineral name of the vermiculite is from Latin, the meaning with " worm's form ", " worm's mark shape ". it is the kinds of mineral hydrous magnesium aluminium silicate mineral iron, which Chinese calls vermiculite the crooked mineral as leech. it is formed, grown and weathered function or hot liquid alteration by black (gold) glimmer, chemical composition (Mg、Fe、AL) 3[(Si、AL) 4O10(OH)2]·4H2O but often change. The shape is brilliant monocline, usually take the form of film, which color is Brown, yellowish-brown or bronze-colored. Oil gloss. Hardness 1~1.5. Density 2.4~2.7g/cm3, the shape of the vermiculite has two kinds of thickness, the thick one is transformed by black (gold) glimmer,etc. keep the characteristic of glimmer slice or scale's flaky; the thin one takes the form of soil. It is so difficult to distinguish mixed with other clay mineral, when roasted for 0.5~1.0 minutes at 800~1000 ℃, the volume swells rapidly, increase 8~15 times, the high one can be up to 30 times. average unit weight is 100~130Kg/m3 of expand vermiculite. Because of roast, the function of expand vermiculite have tiny air separate layer, so have fine warm-keeping performance.