John Villasenor, age 12, of Reno, Nev., for his question:
A ruby is the red gem variety of the aluminum oxide mineral called corundum. It is the rarest and costliest of the gems.
The ruby can sometimes be found in North Carolina, but unfortunately the quality is not good. The world's best rubies come from Burma, with others of good quality coming from Sri Lanka and Thailand.
A perfect Burma ruby may be worth several times as much as a diamond of the same size.
Garnets are often sold under misleading names such as Arizona ruby and Cape ruby.
Millions of carats of synthetic rubies are made each year for use as gems. Their value is as low as a few cents a carat, but they have not hurt the market for the real stone. Experts can easily tell the synthetic product from the natural stone.