This precious stone occurs as a red, transparent variety of the mineral corundum. The color varies in different specimens from rose red through so-called ruby red and carmine to a deep purplish red, called pigeon's blood red. Clear stones of the deeper shades are the most highly prized. When cut cabochon, some specimens exhibit asterism, that is, a six rayed star can be seen in the interior of the stone. Such rubies, called star rubies, are also highly prized.

Many stones which are not rubies are designated by the name. Balas ruby, for example is a type of spinel; Bohemian ruby is rose quartz; Siberian ruby is red or pink tourmaline; American ruby, Cape ruby, Montana ruby, and Rocky-Mountain ruby are varieties of garnet. The finest rubies are found in central Burma in the neighborhood of Mogok, where rubies have been mined since the 15th century.

Important deposits of rubies are also found in Thailand, Afghanistan, Ceylon, India, China, and Russia. Large, clear rubies from Burma and Thailand are much more valuable than diamonds of equivalent size. In the United States rubies are mined in North Carolina, and near Helena, Montana.

In addition to their importance as highly prized gems, rubies are used in industry as jewelry bearings in watches and scientific instruments. Synthetic rubies were first produced in 1837 by fusing alum and chromium-oxide pigment at a high temperature. Improvements in the manufacture of synthetic rubies since then have made possible the production of synthetic stones, which are so like the natural stone in physical and chemical properties that an experienced eye and optical equipment are needed to distinguish between them. In synthetic rubies, air bubbles, which are formed and trapped during the cooling of the molten mass of material, tend to be perfectly spherical in shape. Striations present in the natural stones are straight lines, whereas striations in synthetic rubies are generally curved. Synthetic rubies are used as gems, but about 75% of the annual production of synthetic rubies are used in the manufacture of watches and instruments.

Rubies are made in an apparatus resembling an oxyhydrogen torch. The flame is directed into a fireclay support inside an insulated chamber. The oxygen gas carries finely powdered pure aluminum oxide mixed with 5 to 6 percent chromium oxide into the flame, and the powder fuses into droplets, forming a cylindrical boule or matrix on the support. The size of the resulting ruby is controlled by varying the gas flow, temperature and amount of powder.

Colors other than red are produced by adding different metallic oxides. Stars can be added to synthetic rubies and sapphires by adding an excess of titanium oxide to the aluminum oxide powder and heating temperatures to greater than 1832 F. In gems made with this technique, synthetic stars appear sharper than naturally occurring stars.

Gem cutting, shaping and polishing of gem materials to enhance the beauty of their appearance and in some cases to remove flaws and imperfections. The expert workers who perform these operations are known as lapidaries. Their trade, although highly skilled, is not as exacting as that of a diamond cutter.

Magic and Myth

Rubies are the gemstone of prophecy. In the old days people believed that a ruby would darken when its wearer was in danger. In the 15th and 16th centuries, rubies were thought to counteract poisons so were much in demand. Throughout history, Rubies were thought to bring back or restore youth and vitality when rubbed on the skin.

A powerful and energetic stone, ruby stimulates the life force and brings the light of the Universe into the darkened recesses of the soul. Ruby has been used for many purposes over the centuries. It helps maintain courage, shields and protects the wearer on all levels, and brings lucidity and gentleness of thought and action, it can be used to manifest wealth and to stimulate the sex drive.