(Summary description)Corundum, whose name comes from India, is a mineralogical name. There are three main variants of the homogeneity of corundum Al2O3, namely α-Al2O3, β-Al2O3, and γ-Al2O3. The hardness of corundum is second only to diamond.

Corundum is mainly used for abrasive materials, watch and mechanical bearing materials. Ruby-based artificial crystal as a laser emitting material. Rubies and sapphires are both corundum minerals. Except for the starlight effect, only translucent-transparent and brightly colored corundum can be used as gemstones. The red color is called ruby, while the other colors of corundum are collectively called sapphire in business.

Corundum is a gemstone formed from the crystals of alumina (Al2O3). Corundum mixed with metallic chromium is bright red and is generally called ruby; while blue or colorless corundum is generally classified as sapphire.

Crystal morphology

It is formed under the conditions of high temperature rich in aluminum and poor in silicon. In the endogenous process, it is produced in magmatic rocks and pegmatites rich in aluminum and poor in silicon, and symbiosis with feldspar and spinel. In metamorphism, those produced in gneiss symbiosis with skarn, magnetite, muscovite, etc.; those produced in the contact zone of magmatic rock and limestone symbiosis with calcite, magnetite, epidote, etc. The product of magmatic rock desilication. It belongs to the trigonal crystal system, and the crystal form is often intact hexagonal columnar or barreled. Oblique stripes or horizontal stripes are often developed on the cylindrical surface. Triangular cracks are sometimes seen on the bottom surface; the aggregates are granular.

The main causes of corundum are as follows:

(1) The conditions of high temperature and high pressure formed in the mantle are ejected from the surface with magma.

(2) Formed by contact metamorphism.