Heather Cote - Azure Accessories, August Birthstone - Part IMonday, August 06, 2012 by: Baytoday Business WireFeature - BayToday.ca
- By Heather Cote
Birthstone of the Month
August ~ Peridot (Olivine)
This striking green stone is also called Chrysolite and in the mineralogy world it is known as a variety of stone from the mineral family 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, any shades of brown decrease the value of the stone.
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.
Most of the worlds Peridot, 80 to 95%, come from the San Carlos Reservation in Arizona, being mined by the Native Americans…finer quality gems come from Myanmar (formaerly Burma) and Egypt.
Other locations where peridot can be found are Australia, Brazil, China, South Africa, Hawaii, New Mexico and Zaire.
I'm including the definitions of igneous and metamorphic rocks as I think it helps to understand what these words mean...
"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 re-crystallization, or they can be inherited from pre-existing beds in sedimentary rocks or pre-existing layers in igneous rocks.
The precious minerals can form as the result of re-crystallization when the rocks undergoing metamorphism are subjected to changes in pressure and temperature.
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, formed in the earth’s mantle, 20 to 55 miles inside a volcano…they are found in 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.
In other words it is found in the rocks formed by volcanoes.
The striking green color of the peridot comes from 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, and small crystals of pyrope garnet and spinal.
While lovely, the peridot is not a brilliant stone, it may have the appearance of glass or even look greasy…the stone may have a cat's eye or star effect but this is extremely rare.
Treatments, such as oiling or 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, hair spray, etc.
Stones of Interest:
• A 319ct peridot 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.
• 192.75 carat peridot stone belonging to the Czar is in the Diamond Registry in Moscow
Information of Interest:
• Historians wonder if the gems worn by Cleopatra were actually peridot and not emeralds…
• Some wear this stone as they believe it brings success, peace and good luck
• It is the gift for the 16th wedding anniversary.
• It is one of the few stones that comes in one color only
• In ancient Egypt on an island called Zeberget mining for peridot was done at night as it was said the gemstone couldn’t be seen well during the day.
• I’ve seen the phonetic spelling as per-i-doe and per-i-dot…so not sure which is correct, I do think both are accepted.
• Associated with light
• Generally a transparent gem
• Ancient records document peridot being mined back as far as 1500 B.C.
• While it can be…this stone is generally not treated or enhanced
• Relatively inexpensive in price
• All be it rare, peridot have also been found in meteors
• Avoid ultrasonic cleaners, mild soap and water will clean this stone
• Cracks easily so be gentle with it…
Don’t forget…send any questions or comments to the following email address…
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End of Part I
August 6th, 2012 - Part II