Abstract: Different types of perlite have been found in the Yingcheng coal mine，Jiutai . Based on the composition and structure, perlite in the mine can be classified as strong altered, rhyolitic structure, rhyolitic and pearl structure interbedded, porphyroblast containing and silicated perlites. According to their altered stages and products, perlite in the mine can also be classified as unaltered(normal), weak montmorillonitized, strong montmorillonitized and silicified-montmorillonitized perlites. The formation processes of the perlite in the area could be suggested as the followings: after being exhausted on the surface, the lava falls into water directly, where it was condensed and consolidated because of plastic glass hydration. And its alteration process was promoted by the presence of the alkaline aqueous medium. The perlite in the area is of characteristics of decreasing reservoir significance with increasing alteration.

Key words: Yingcheng coal mine, Jiutai, Yingcheng Formation, perlite, genesis, alteration mechanism