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: Peridot

Peridot Gemstones used in Jewelry

Source: Burma (Myanmar), Egypt, Norway, Pakistan, Saudi Arabia, Sri Lanka, USA (Arizona, Hawaii)

Birthstone: August

The name "peridot" (péridot French, peridoto Spanish or Italian), means "golden stone" in Greek (peridona); and is also derived from the French word "peritot," meaning "unclear" due to significant amounts of inclusions that are typical in the stone. Golden-yellow peridot also goes by the name "chrysolite."

Peridot, also known as the "evening emerald," was treasured by the Egyptian Pharos, and some of Cleopatra's "emeralds" were actually peridots. In the Middle Ages, people wore peridot to gain foresight and divine inspiration, as well as to protect them against evil.

Peridot Mining

Peridot mining dates back some 4,000 years. Ancient olivine peridot mineral deposits located on Saint Johns Island off the coast of Egypt in the Red Sea were documented by the greek historian Pliny the Elder (below, left) in his book Naturalis Historia (Natural History) in AD 70. Those ancient deposits on Saint Johns Island, now named Zabargad Island (below, right) still produce high-quality peridot stones, although most modern Peridot comes from the United States in Arizona. One of the largest faceted peridot gems in the world (Smithsonian Institution collection) is a 311.8 carat (62 g) stone found on Zabargad.

Pliny the Elder's Naturalis Historia

Peridot Mines on Zabargad Island, Egypt

Peridot, also called precious olivine (magnesium iron silicate), is a transparent green variant of forsteritic olivine associated with peridotite, a dense mafic or ultramafic igneous rock. Peridot crystallizes in the orthorhombic crystal system, with a "granular mass" crystal habit, usually resulting in rounded pebbles; or in short, vertically-striated prisms. Peridot is classified as a Nesosilicate in the Silicate mineral group.

Olivine is a mineral that composes a lot of the earth's mantel, which is the layer just below the outer crust. Olivine is also common in basalts found on the moon. Peridot was called "Topazion" until the 18th century when the British renamed it Peridot. Today, the highest quality peridot is typically mined in Pakistan, and is called "Kashmir Peridot" or "Cashmir Peridot."

Peridot (Precious Olivine) Crystallography, Chemistry, Physical Properties

Peridot (Precious Olivine) Optical Properties

Peridot is a gemstone variety of forsterite, the magnesium-rich end of the olivine series. Chrysolite is a golden yellow variety of peridot. Peridot is ideochromatic, getting its distinct green coloration from ferrous iron which is a natural part of its crystal lattice structure. Higher quality peridot generally contain about 10 to 15% iron.

Transparent green olivine peridot (right) and a Peridotite druzy encrustation embedded in a basalt matrix commonly found in lava fields. Transparent olivine is usually found in arid climates such as Arizona, Egypt (Zabargad), Saudi Arabia and Pakistan (Suppatt district) due to its susceptibility to decay when subjected to weathering and rain.

Peridot Treatments & Care

Peridot is not usually enhanced or heat-treated but it is occasionally treated with colorless oils, wax, and natural or synthetic resins to fill in voids or surface fractures, and to improve appearance or surface luster.

Peridot (Precious Olivine) Crystals

Peridot Necklace

Peridot has a lower durability than many other gemstones, and when a faceted peridot is set in a ring with a prong setting extra care should be used. Peridot is also subject to thermal shock, therefor you should never clean peridot jewelry in an ultrasonic cleaner due to its tendency to fracture. Similarly, you should avoid the use of a steam cleaner as rapid changes in temperature may cause fracturing.

Bibliography and Reference on Peridot

Judith Crowe, The Jeweler's Directory of Gemstones . DK Publishing.

The Mineralogical Record, A Mineral Collector's Knowledge Database www.minrec.org

Cally Hall, Smithsonian Gemstones . Simon & Schuster.

Walter Schumann, Gemstones of the World . NAG Press; 2Rev Ed edition

Renee Newman, Gemstone Buying Guide . International Jewelry Publications; 2nd edition

Antoinette L . Matlins, Antonio C. Bonanno, Gem Identification Made Easy . Gemstone Press

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