Other Free Encyclopedias » 21st Century Webster's Family Encyclopedia » 21st Century Webster's Family Encyclopedia - Constance Missal to Crete



Corundum, mineral consisting of alumina (aluminum oxide, Al2O3) and second in hardness only to diamond. It forms precious stones, such as rubies, sapphires, topaz, amethyst, and emerald; the “jewels” in watches and instrument bearings are often made of corundum. Because of its hardness, corundum is widely used in emery and other abrasives. Corundum is found in many countries, often in association with quartz.

Bill Cosby [next] [back] Cortisone

User Comments

Your email address will be altered so spam harvesting bots can't read it easily.
Hide my email completely instead?

Cancel or