August's birthstone is famous for its vibrant green color, but perhaps its most fascinating feature is the crazy backstory associated with its name. Believe it or not, for nearly 2,000 years, the gemstone we now know as peridot answered to the name topaz. Then, in one of gemology's most curious twists, that familiar name was reassigned to a completely different gemstone family, leaving the original "topaz" in search of a new identity.
The story of how August's birthstone became known as peridot is filled with unexpected turns, unanswered questions and more than a little linguistic intrigue.
Ancient Egyptians mined the vibrant yellowish-green gem on a small Red Sea island known to the Greeks and Romans as Topazios, just off the coast of Egypt. To honor its place of origin, they named the gemstone topazion, a name that was eventually shortened to simply topaz.
Here's where the story takes a curious turn.
Sometime during the 18th century, mineralogists reassigned the name "topaz" to an entirely different gemstone family — the one we recognize today in shades of blue, golden yellow, pink and other colors. The original "topaz" suddenly needed a new identity, and the ancient green gem became known as peridot. Why the name "topaz" was transferred remains something of a mystery, making this one of gemology's more intriguing cases of mistaken identity.
Ironically, the island that gave topaz its name never produced a single topaz crystal.
Even the word peridot has an uncertain origin. Some scholars believe it derives from the Arabic "faridat," meaning "gem," while others trace it to the Old French "peritot." Still other theories point to Greek or Latin roots. More than two centuries after the name change, experts still can't agree on its true linguistic ancestry.
The accompanying image showcases perhaps the most famous peridot in existence — a spectacular 311.80-carat faceted gem from Zabargad, the modern Arabic name for ancient Topazios. According to the Smithsonian's National Museum of Natural History and gemologist Jeffrey Edward Post in his book Unearthed: Surprising Stories Behind the Jewels, it is believed to be the largest faceted peridot in the world. Donated to the Smithsonian in 1926 as part of the famed Roebling Collection, the extraordinary gemstone is said to have adorned the image of a saint in an Austrian church for several centuries before entering the museum's collection.
Peridot's story is every bit as remarkable as its name. The gem is the transparent variety of the mineral forsterite, a magnesium-iron silicate whose signature green color comes from iron atoms replacing some of the magnesium in its crystal structure. Too little iron produces pale stones; too much creates undesirable brownish tones. The most prized peridots display a rich, saturated green with only slight hints of yellow and no brown.
Unlike most gemstones, peridot forms deep within the Earth's mantle, roughly 20 to 55 miles below the surface. Scientists have even identified peridot in meteorites and on Mars, making August's birthstone not only ancient, but truly out of this world.
Credit: Photo by Chip Clark and digitally enhanced by SquareMoose / Smithsonian.