Peridot, the gem form of the mineral olivine, traces its jewelry roots back more than 3,500 years. It was first mined by the ancient Egyptians on the island of Zebargad in the Red Sea. Zebargad was known as the "serpent isle" because it was infested with snakes that interfered with mining activity until one Pharaoh finally had them all driven into the sea.

Found in various shades of green, peridot is most prized in lime hues. The Romans called peridot "evening emerald" because its green color was said to glow at night. The gem was also used to decorate medieval churches and was most likely carried back to Europe by the Crusaders. Large peridots of more than 200 carats in size adorn the shrine of the three magi at the Cologne Cathedral in Germany.

Small crystals have been found in volcanic rock - in fact, Hawaiian legend called peridot the divine tears wept by Pele, goddess of the volcano. Samples of the gem also have been discovered in meteors that have fallen to earth.

The ancients believed that peridot had the power to ward off evil spirits, nightmares and enchantments. It was also used as a medical remedy to treat asthma and other ailments. Its power was considered most potent when the stone was set in gold. Peridot was also said to strengthen any medicine drunk from goblets carved from the stone.

Most of today's peridot is mined by Native Americans on the Carlos Reservation in Arizona. It is also mined in Brazil, China, Egypt, Germany, Hawaii, Italy, Norway, Myanmar, and Sri Lanka. A new deposit was discovered in Pakistan in 1994, yielding some of the finest peridot ever seen. Numerous fine, large crystals were discovered, including one stone of more than 300 carats.

Peridot is readily available in a range of sizes, shapes and color hues. The finest stones are eye clean and have a deep, lime green color. Because inclusions are common, clarity is an extremely important factor when buying peridot.

Its relative affordability and lively green color has made it a popular substitute for those who cannot afford emeralds. The birthstone for August, peridot is also the recommended gem for couples celebrating their 16th wedding anniversary.

When shopping for peridot, keep in mind that it is relatively soft (6.5 on the Mohs hardness scale) and should be spared rugged, regular wear if mounted in a ring. This is why the gem is more often used as a sidestone for more expensive gems than as the center stone. It is also highly sensitive to rapid temperature changes and can lose its polish if brought into contact with hydrochloric or sulfuric acid.

Peridot is occasionally treated with colorless oil or wax to improve its appearance. Surface fractures are sometimes filled with a colorless resin that hardens. If done properly, these treatments should remain stable.

Fine large specimens of the stone are on display at the Smithsonian Institution in Washington, D.C.; the Diamond Treasury in Moscow; and the Geological Museum in London.