Ann: Mustang Achieves Record Month of Production, page-29

Commercial rubies (corundum) are the third hardest mineral, so can have various commercial uses, including: Industrial abrasives, and are used for grinding media, polishing compounds, sand papers, grinding wheels, and other cutting applications. They are essential in lasers, also used as bearings, and as jewels in watches, etc.

Also rubies are chemically inert and resistant to heat. These properties make it a perfect material for making refractory products.