What is Corundum?

Corundum is a rock-forming mineral that is found in igneous, metamorphic, and sedimentary rocks. It is an aluminum oxide with a chemical composition of Al2O3 and a hexagonal crystal structure.

The mineral is widely known for its extreme hardness and for the fact that it is sometimes found as beautiful transparent crystals in many different colors. The extreme hardness makes corundum an excellent abrasive, and when that hardness is found in beautiful crystals, you have the perfect material for cutting gemstones.

Natural and synthetic corundum are used in a wide variety of industrial applications because of their toughness, hardness, and chemical stability. They are used to make industrial bearings, scratch-resistant windows for electronic instruments, wafers for circuit boards, and many other products.

The extreme hardness of corundum makes it especially useful as an abrasive. Crushed corundum is processed to remove impurities and then screened to produce uniformly sized granules and powders. These are used for grinding media, polishing compounds, sand papers, grinding wheels, and other cutting applications.

Some problems with using natural corundum as an abrasive are that the deposits are usually small, irregular in shape, and the corundum is of variable quality. They are not reliable sources of consistent-quality material needed to run a manufacturing process. Synthetic corundum, produced using calcined bauxite, has become a more reliable source with more consistent properties. It has replaced natural corundum in most manufactured products.

Corundum has many other uses. It is chemically inert and resistant to heat. These properties make it a perfect material for making refractory products such as fire brick, kiln liners, and kiln furniture. Today, these products are usually made with synthetic corundum.