Peridot

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Peridot
General
Category	Mineral
Chemical formula	(Mg, Fe)2SiO4
Identification
Color	Yellow to yellow-green
Crystal system	Orthorhombic
Cleavage	Poor
Fracture	Conchoidal
Mohs Scale hardness	6.5-7
Luster	Vitreous
Refractive index	1.64-1.70
Birefringence	+0.036
Streak	White
Specific gravity	3.2-4.3

Peridot (pronounced "pair-uh-doe", IPA: /pɛɹɪdɑːt/ or Fr. /peʁido/) is the gem quality variety of forsteritic olivine. The chemical composition of peridot is (Mg, Fe)₂SiO₄, with Mg in greater quantities than Fe. The name of the gemstone is believed to come from either the Arabic word faridat meaning "gem" or the French word peritot meaning "unclear." Peridot is one of the few gemstones that comes 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". Olivine is a very abundant mineral, but gem-quality peridot is rather rare. Peridot crystals have been collected from iron-nickel meteorites.

Contents 1 Occurrence 2 History and Lore 3 External links 4 References

[edit] Occurrence

Olivine is a common mineral in mafic and ultramafic rocks, and is often found in lavas and in peridotite xenoliths of the mantle that lavas carry to the surface; however, gem-quality peridot only occurs in a fraction of these settings. Peridot is mined in North Carolina, Arizona, Hawaii, Nevada, and New Mexico, in the US; and in Australia, Brazil, China, Kenya, Mexico, Myanmar (Burma), Norway, Pakistan, South Africa, Sri Lanka, and Tanzania. Peridot of high quality is commercially mined in the eastern lava fields of Saudi Arabia. The largest cut peridot is a 310 carat (62 g) specimen in the Smithsonian Museum in Washington, D.C.. A special variety of a peridot from Pakistan is known as "Kashmir" peridot. Due to the large size of the rough stones found there, cutters have successfully created faceted stones of over 100 carats (20 g) from the rough gems of this area.

[edit] History and Lore

It is the birthstone for the month of August. According to folklore, the peridot will bring its wearer success, peace, and good luck. Peridot has been found in Egyptian jewelery from the early second millennium BCE and was mined from the volcanic island of Zebirget, or St. Johns Island, in the Red Sea.

[edit] External links

• Mineral Galleries - Peridot
• Gemstone.org Peridot
• USGS peridot data
• Emporia Edu
• Florida State U. - Peridot

[edit] References