Peridot is a yellowish green color and is the official birthstone of August. It is also used for the 15th wedding anniversary.
Peridot has been found in comet dust as well as many meteorites with ages potentially dating back to the beginning of our solar system. This makes Peridot the oldest gemstone you can find. Peridot has a consistent yellowish-green color, though, differences in hue and size will determine the value which may vary considerably.
Ancient Egyptians called Peridot "the gem of the sun". It was believed that the stone would glow with the light of the sun even after dark. The name was derived from the word faridat, which is the Arabic word for gem.
Mineral Group: Olivine
Refractive Index: 1.65 to 1.69
Birefringence: 0.035 to 0.038
Specific Gravity: 3.34
Mohs Hardness: 6.5 to 7.0