Cenosphere: A cenosphere is a lightweight, inert, hollow sphere comprised largely of silica and alumina and filled with air and/or gases. Cenospheres are a naturally occurring by-product of the burning process at coal-fired power plants, and they have most of the same properties as manufactured hollow-sphered products. Typical Properties of Cenospheres SiO2: 52 - 62% Al2O3: 32 - 36% K2O: 1.2 - 3.2% Fe2O3: 1 - 2% TiO2: 0.8 - 1.3% MgO: 1 - 2.5% Na20: 0.2 - 0.6% CAO: 0.1 - 0.5%
