... : higher toughness than SiC, Micro hardness 1800-2200 kg/mm², bulk density ≥ 3.85 / cm³, high temperature, high refractoriness 1850°C.Usage ... Index Item IndexColorBrownCrystal shapeTrigonalHardness(mohs)≥9.0Melting Point (°C)2250True density (g/cm3)≥3. 90Linear Expansion Coefficient(0—1600°C)7 ...