When I think of gems, I immediately think "jewelry." But gems are used in many other ways. In fact, the majority of gems that are mined are used in applications other than jewelry. Here are just a few.
Corundum is aluminum oxide. It is called ruby when red and sapphire when other colors. Regardless of color, corundum is used as an abrasive for grinding glass and polishing metal. It is made into sandpapers and grinding wheels.
Jewelry Facets provides more information about these and other gemstones.
Lynn's musings about all facets of jewelry.