... . C)Refractive index e = 1.760 w = 1.768 (Na line)Resistivity 30 C 300 C 900 C 1600 C (cm ... impurities, sparing cleaning trouble. Fine, white corundum used for polishing grinding head. Can also be used to do all kinds of product additive ... , etching processing: jade, crystal, agate, semi-precious stones, seals, and stone, antiques, marble tombstone, ceramics, wood, bamboo piece of etching artists ...