重烧镁砂是选用天然菱镁石，经高温竖窑煅烧而成。它是制造生产不定型耐火材料的理想原料，制品用于炼钢平炉,电炉炉底和捣打炉衬。
 species
| Chemical composition |
LOI％ | SiO2％ | Fe2O3％ | Al2O3％ | CaO％ | MgO％ | BDg/cm3 |
SM-93 | 0.5 | 3.0 | 1.2 | 0.8 | 2.0 | 93 | 3.18 |
SM-92 | 0.5 | 3.5 | 1.4 | 1.0 | 2.3 | 92 | 3.15 |
SM-91 | 0.5 | 3.8 | 1.5 | 1.2 | 2.4 | 91 | 3.15 |
SM-90 | 0.5 | 4.0 | 1.6 | 1.4 | 2.5 | 90 | 3.15 |
SM-89 | 0.7 | 5.5 | 2.0 | 1.6 | 2.5 | 89 | 3.15 |
SM-87 | 0.7 | 7.0 | 2.0 | 1.7 | 3.0 | 87 | 3.10 |
