Bright black powder with less than 2% of semitransparent and/or whitish crystals SIZES (US mesh - stock ... /270, 270/325, 325/400, 400/500SIZES (microns - stock items): 2-4, 4-8, 8-12, 10-14, 14-20, 15 ... /cu.sm.Impurities (max % mass): Mg - 2.0%, C - 0.4% , a-BN - 0.2%, others - 0.2%Heat Resistance: High CUBIC BORON NITRIDE ...