How a Peridot Gem Is Formed
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What is a Peridot?
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The peridot is a gemstone prized for its distinctive, dazzling yellow-green color. It's also the birthstone for August, thought to bring good luck and fortune to the wearer born during the month of its glittering reign. According to the U.S. Geological Survey, peridots have been worn in jewelry for thousands of years, and some even think that some of Cleopatra's many "emeralds" may actually have been peridots.
Peridots are usually only found in small amounts (stones that can be cut up to 1 to 3 carats), and have a long process of formation. The journey from drab minerals to shimmering jewelry involves a long geological process before the stone reaches the gem cutter's hands.
Olivine, Peridot's Mineral Source
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According to the U.S. Geological Survey, the peridot is a form of olivine, a silicate mineral rich in magnesium and iron. It's primarily mined commercially in the United States in Arizona and New Mexico.
The University of California at Berkeley identifies olivine as being yellow to pale green or even black in color. Olivine is found in many different rocks such as basalt, volcanic rock and even the earth's mantle--which is made mostly of olivine.
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From Olivine to Peridot
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When olivine crystallizes, it turns into the gemstone form we know as the peridot. This process involves long periods of high temperature and pressure within the rocks in which the mineral is found, and occurs on geological time-scales--sometimes millions of years.
Olivine has a very high melting point, which explains why it's mainly found in places like volcanic rock and the mantle of the earth (where pressure and heat are abundant). In these deep, hot places, the gem we know as the peridot is slowly formed.
How the peridot gets its distinctive color depends on the composition of the olivine. Olivine with a high magnesium content produces a paler stone; iron-rich olivine crystallizes into a darker, richer peridot.
Once crystallized, the peridot waits only to be mined, cut and set into a piece of jewelry to be admired and prized as a birthstone--or a striking addition to a jewelry ensemble.
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Resources
- Photo Credit Peridot gems (public domain photo courtesy of the U.S. Geological Survey)
