... 250 - 450kg /m3,granularity diameter is about 1 mm , Hollow glass micropheres is a hollow ball collected from coal powder,its ... of the hollow galss microsphaeres mainly contains SiO2 and Al2O3, with fine particles ,hollow, high strength and durable, resistant to temperature ... ,80-120 mesh,150—200 mesh,over 200 mesh Hollow Glass Microspheres Collected From Coal Powder