August's birthstone Peridot is the gem variety of olivine. A transparent-translucent gemstone in colors of green, yellow-green, and olive. Peridot has been mined as a gemstone for thousands of years. Egyptians were mining green stone from the Isle of Zabargad (also called The Isle of St. John) in the Red Sea in about 1500 BC. Peridot is found on Topazios, an island in the Red Sea. It was probably originally named topaz. A major source of this gem in the U.S. is Arizona.