The commonest sort of crystalline alumina, α-aluminium oxide, is named corundum. When trace things make it look red it is called ruby, but all other colorations drop beneath the designation sapphire. Corundum has a trigonal Bravais lattice with an area group of R-3c (number 167 during the Intercontinental Tables). Cerium https://landenpsvbc.ourcodeblog.com/35043824/facts-about-diamond-revealed