"Birthstone of the Month" Peridot (Olivine)

This striking green stone is also called Chrysolite and in the mineralogy world it is known as Olivine. It is thought the name Peridot comes from the Arabic word faridat which means "gem". This beauty only comes in various shades of green, pale yellowish green, olive green, bottle green or a vibrant apple green, which is the most sought after. In Pakistan, near the Afghan border you will find large Kashmir peridot stones which are the best for cutting, possessing intense striking color, which of course makes them expensive. Other locations where peridot is found is, Australia, Brazil, China, Egypt (St.John's Island), Myanmar (formerly Burma), South Africa, United States (Hawaii, Arizona) and Zaire.


I'm including the definitions of igneous and metamorphic rocks as I think it helps to understand what these words mean...

Metamorphic Rocks
"The American Heritage Science Dictionary: 1. Relating to metamorphosis. 2. Geology: Relating to rocks that have undergone metamorphism. Metamorphic rocks are formed when igneous, sedimentary, or other metamorphic rocks undergo a physical change due to extreme heat and pressure. These changes often produce folded layers or banding in the rocks, and they can also cause pockets of precious minerals to form. The folds and banding can be produced by incomplete segregation of minerals during recrystallization, or they can be inherited from preexisting beds in sedimentary rocks or preexisting layers in igneous rocks. The precious minerals can form as the result of recrystallization when the rocks undergoing metamorphism are subjected to changes in pressure and temperature.

" Igneous: "
adjective
1. Geology...produced under conditions involving intense heat, as rocks of volcanic origin, or rocks crystallized from molten magma. 2. of, pertaining to, or characteristics of fire.

Intrusive Igneous Rock: forms beneath the surface of the volcano
Extrusive Igneous Rock: forms on the surface volcano"

Peridot, which is an extrusive igneous rock forms as a result of magma reaching the surface of the volcano, either from eruption, or cracks, fissures or as lava or ash. It can also form in metamorphic rocks. The striking green colors of the peridot comes from its own chemical composition of the stone (iron) itself and not from some other sources such as impurities. Peridot is transparent but often includes some form of inclusion, they appear as spots or lines, and are naturally occurring deposits of such things as silica glass, biotite mica, small crystals of pyrope garnet and spinel. While lovely, the peridot is not a brilliant stone, it may have the appearance of glass or even look greasy, rarely, the stone will have a cat's eye or star effect. Treatments, such as oiling or a polymer filler may be used to improve the look of the stone, by decreasing the visibility of flaws. Care must be taken with the peridot as it is tends to burst under pressure, it is sensitive to heat and is not resistant to acids...so keep away from household cleaners, steam, etc.


Stones of Interest:

• A 319ct perito found on the island of Zabargad is now in the Smithsonian Institution in Washington DC.
• Cut stones from a meteorite that fell in 1749 in eastern Siberia are now in Russia.

As always, I hope you found the Peridot information interestingly informative!!
Cheers


Information courtesy of: Gemstones of the World,Walter Schumann, Third Edition, Sterling Publishing Co., The Jeweler's Directory of Gemstones, Judith Crowe, Firefly Books, 2006 "igneous." dictionary.com Unabridged (v 1.1). Random House, Inc. 21 Aug. 2008. dictionary.com http://dictionary.reference.com/browse/igneous "metamorphic" The American Heritage® Science Dictionary. Houghton Mifflin Company. 21 Aug. 2008. dictionary.com http://dictionary.reference.com/browse/metamorphic
The two photos of the raw peridot are courtesy of @Edith Ochs - Fotolia.com, thank you.
The lovely peridot ring photo is courtesy of @K. Geijer - Fotolia.com, thank you.