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August Birthstone: Peridot Is a Deep-Earth Gem That’s Also Out of This World

August’s vibrant green birthstone, peridot, has the distinction of being one of only two gems that form in the Earth’s mantle. The other is diamond.

While most other gems crystallize in the Earth’s crust, three to 18 miles below the surface, peridot forms in the Earth’s upper mantle, about 20 to 55 miles deep, and is blasted to the surface by volcanic activity.

And while peridot is considered a deep-Earth gemstone, it’s also out of this world — literally.

August’s birthstone has been found scattered across the surface of Mars, as well as embedded in meteorites that have crash-landed on Earth.

The extremely fine, Pakistan-sourced 46.16-carat gem (shown above) is part of the Smithsonian’s National Gem Collection in Washington, DC. The barrel-cut gem — a 2009 gift from David Villwock and Daniel Sarros — displays peridot’s coveted grass green color. It’s a pure hue without strong undertones of yellow or brown.

Peridot claims a curious origin story that takes us back to the Egyptian island of Topazios in the Red Sea around 300 BC. The ancients believed the green gems mined on the island possessed protective powers and anointed them as the “gems of the sun.” They called the stones “topazion” to honor their place of origin and, eventually, the name was shortened to “topaz.”

And that’s the way it was for more than 2,000 years.

Then, for reasons that the Smithsonian claims are still unclear, the name “topaz” was hijacked during the 18th century and assigned to the gem we call topaz today. The ancient green stone would be renamed peridot, which is derived from “faridat,” the Arabic word for gem.

Ironically, the historic island of Topazios (now called Zabargad or St. John’s Island) has never yielded a single topaz.

Today, the gem we know as peridot can be found on five continents. Important sources include Myanmar, the US (Arizona), Norway, Brazil, China, Australia, Antarctica and Pakistan.

Peridot is the gem variety of the mineral forsterite. Pure forsterite is colorless, but iron atoms replacing some of the magnesium produce the green shades. Peridot is one of only a few gemstones that occurs in just one color.

In addition to being an official birthstone of August — along with spinel and sardonyx — peridot is the 16th anniversary gemstone.

Credit: Photo by Ken Larsen / Smithsonian.

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