Peridot: Birthstone for August
Peridot is gem-quality olivine, which is has the chemical composition (MgFe)2SiO4. The beautiful green color results from the presence of iron; the higher the iron content, the richer the quality of green. Peridot has often been mistaken for emerald, which is a variety of the mineral beryl (Be3Al2SiO6). The two gems can be separated by their differences in hardness: emerald has a hardness of 7.5-8 on the Mohs scale, while peridot has a hardness of 6.5-7.
Peridot is generally found in basalt, which is brought to the surface of the earth by volcanic activity. Olivine is a common mineral, which accounts for the widespread distribution of peridot: small-sized specimens can be found in the United States, China and Vietnam, while the largest crystals of peridot occur in Finland, Pakistan, Myanmar (Burma) and the island of Zabargad. The last-mentioned locality, Zabargad, has a very long association with peridot. Located in the Red Sea near Egypt, the island of Zabargad was heavily mined by the ancient Egyptians, and this has caused historians to believe that some of Cleopatra’s famous emeralds may in fact have been peridot. The island was later renamed St. John’s Island, and is currently known as Zabargad.
In more recent times, fine specimens of peridot have been mined in Myanmar (formerly Burma), with outstanding size (20-40 carats), color and clarity, but the political situation in that country has severely curtailed worldwide access to the Burmese gem market.
Peridot has also been found in certain meteorites (known as pallasites), and in some instances, crystals suitable for use in jewelry have been obtained. These extraterrestrial gems are truly ancient, having been formed approximately 4.5 billion years ago, concurrent with the origin of our solar system.
According to the United States Geological Survey (USGS), the United States was the leading producer of peridot for many years, but China and Pakistan are producing increasing amounts of the gems. Most of the United States peridot production takes place in Arizona, and in fact the Peridot Mesa (San Carlos Apache Indian Reservation, in Gila County) is ranked by the USGS as “the most productive locality for peridot in the world,” accounting for 80-95% of the world’s production of peridot. Small quantities of peridot have also been found in New Mexico.
What should a buyer look for, when purchasing a peridot? According to the Gemological Institute of America, “the finest hue is green without any hint of yellow or brown. The gem’s colors tend to be their finest in stones weighing 10 carats and above. Lower-quality peridot is brownish.” The choicest stones are an intense pure green, and are predominately found in Myanmar and Pakistan; these countries also are the source of the largest stones. In terms of clarity, better-quality stones are always eye-clear, although inclusions will be visible under magnification. Peridot is available in a wide variety of cuts and styles.
Peridot is the fifteenth anniversary gemstone, and the birthstone for August.
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