August Birthstone: A Historical and Geological Perspective
The August birthstone is represented by three gemstones: peridot, spinel, and sardonyx. Of these, peridot is the most widely recognized and studied. This gemstone is unique in that its color—ranging from yellowish-green to olive and brownish-green—is intrinsic to its chemical composition rather than the result of trace impurities. The presence of iron in the mineral determines the intensity of the green hue.
The name "peridot" is believed to originate from the Arabic word "faridat," meaning "gem." Some scholars suggest an alternate derivation from the Greek word "peridona," meaning "giving plenty," which aligns with the gemstone’s historical association with prosperity and good fortune. In ancient times, peridot was considered a protective talisman, used to shield the wearer from evil spirits and "terrors of the night."
According to historical records, peridot was highly valued in many ancient and medieval cultures. It appeared in the jewelry of priests as early as the second century BCE and later in the chalices and churches of medieval Europe. The gemstone was especially prized in ancient Egypt, where it was mined on the island of Zabargad, also known as Topazios, in the Red Sea. The island was known to the Greeks and Romans as Topazios, and the gemstone was originally referred to as "topazion" until the 18th century, when the name was mistakenly assigned to the gem we now know as topaz.
Peridot forms deep within the Earth’s mantle and is brought to the surface by volcanic activity. Interestingly, it has also been found in meteorites, making it one of the few gemstones with an extraterrestrial origin. Peridot can be found on five continents, with major sources including Burma (Myanmar), the United States (Arizona), Norway, Brazil, China, Australia, and Pakistan. The San Carlos Reservation in Arizona is a particularly significant source of the gemstone, contributing much of the world’s supply.
Peridot has a unique property known as double refraction, which means that under close inspection, two images of each facet may be visible. High-quality peridots are typically free of visible inclusions, though microscopic examination may reveal small imperfections. The finest specimens of peridot are found in prestigious museums, including the Smithsonian Institution in Washington, D.C., which houses a remarkable 310-carat gemstone.
Sardonyx, another August birthstone, is a composite of sard and onyx, two varieties of chalcedony. It is characterized by its reddish zebra-striped pattern with white bands. The name sardonyx is derived from the city of Sardis in present-day Turkey, where the red sard was found, and the Greek word "onyx," meaning "nail or claw." The coloration of sardonyx depends on the presence of iron oxide, which can range from yellowish-red to reddish-brown.
Peridot is relatively affordable in smaller sizes due to rich deposits discovered in Pakistan during the 1990s. However, larger stones command higher prices, with the finest quality specimens being rare and highly sought after. Commercially mined peridots typically measure between six to 13 millimeters, with faceted stones averaging about one carat in size.
In conclusion, the August birthstone, particularly peridot, holds a rich historical and geological significance. Its unique properties, historical uses, and sources make it a gemstone of enduring appeal and value. The documentation provides a comprehensive overview of peridot’s origins, characteristics, and cultural importance, making it a valuable resource for those interested in the history and properties of gemstones.