vermiculite fall into two kinds,goden expanded vermiculite and silver white vermiculite. the unit weight of vermiculite is 100-300kg/m3, the ph value: 7-9. one stere of vermiculite can absorb 500-650 liters water. after sterilizing by high temperature vapor, it can emit some kalium, calcium, and magnesium. there are abundant nitrogen, phosphor, kalium, aluminum, ferrum, magnesium, and silicate in it. with abundant layer charges, the vermiculite has the high qualities of cation exchange and cation exchanging adsorption. its characteristics are: light, good at adsorbing the water and fertilizer, undecomposable, can persist 3-5 years (different from the humus or the shell of coconuts).