Kyanite is unusual in that its hardness varies, depending on the direction of the crystals. Some of the crystals are similar to blue sapphires and are used as gemstones. Kyanite is also used in the making of the frequently used industrial compound mullite. This compound has the chemical formula...
ofvariousminerals,mineralandrockarecloselyrelated;(2) therockisthematerialbasisofgeologicalstructureand landform;(3)researchisthehistoricalbasisofcrustal rocks. (igneousrock)alsocalledigneousrock".Fromthedepthsof theearth'scrustormantlemeltingmagma,influencedbysome ...
brake disks, abrasives, heating elements as well as lighting, and electrical power systems. The natural type of silicon carbide is prized as a jewel because it has the same appearance and hardness as diamonds. It is an artificial substitute that is harder compared to zirconia. ...