Peridot (pronounced pear-a-doe) is the gem quality variety of forsterite olivine. It is bright yellow-green in color, and has a hardness of 6.5 on Mohs scale. The chemical composition of peridot is (Mg, Fe)₂SiO₄. Peridot is one of the few gemstones that come in only one color. The depth of green depends on how much iron is contained in the crystal structure, and varies from yellow-green to olive to brownish green. Peridot is also often referred to as "poor man's emerald". The name of the stone possibly derives from the French peritot, meaning unclear, due to the many inclusions and cloudiness of larger stones.

A special variety of peridot from Pakistan is known as "Cashmere" peridot, due to the large size of the rough stones found there. Cutters have successfully created faceted stones of over 100 carats from the rough gems of this area.

It is the birthstone for the month of August. According to folklore, the peridot will bring its wearer success, peace, and good luck. Its powers supposedly include protection, health, and sleep and it is used to attract love and calm anger while also soothing nerves and dispelling negative emotion. Rumor has it that peridot was the favorite gemstone of Cleopatra.