A porous, lightweight, siliceous sedimentary rock composed of the shells of diatoms or radiolarians or of finely weathered chert, used as an abrasive and a polish.是什么意思_A porous, lightweight, siliceous sedimentary rock composed of the shells of diatoms or radiolarians or of finely weathered chert, used as an abrasive and a polish.在线翻译_英语_读音_用法_例句