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Roger Weller, geology instructor

wellerr@cochise.edu


Olivine
by Gina Bays
Physical Geology
Spring 2007
     

Olivine-Emerald of the Evening 
 

I was born and raised in Globe, Arizona.  Globe is located just west of the San Carlos Apache Indian Reservation.  Being in such close proximity to the reservation provided cultural and gemological benefits.  One of these benefits was the ability to purchase the gemstone peridot very easily. 
 

Peridot (pronounced pair-a-doe), comes in varieties of light yellowish green, to intense bright green, to an olive color.  Its natural beauty almost seems to glow.  Peridot is a translucent to transparent gemstone.  It ranges between 6.5 and 7 on Mohs scale of mineral hardness.  Peridot is the gem variety of the mineral Olivine (Mg,Fe)SiO4 (Bernardine).
 

Photo of Olivine in Basalt

Photo Courtesy of R Weller/Cochise College

 

Peridot is mined out of volcanic ash, specifically out of the volcanic rock known as basalt.  It has been mined in many areas of the world including Burma, Germany, Brazil, Egypt, New Mexico, California, Arizona, Hawaii, and Pakistan.  Gem quality peridot is mined mostly in large quantities on the San Carlos Apache Indian Reservation in Arizona.  It is rumored that the largest deposits in the world are located in this area.  The peridot is mined mainly in an area referred to as Peridot Mesa.  On the Peridot Mesa the olivine stones are located within a layer of basalt which is about nine to over one hundred feet deep.  The olivine is recovered both after it has naturally weathered out of the basalt layer and by drilling and blasting deep into the basalt layer.  Stones between one carat and four carats are common.  Stones five carats and over are much more valuable and increase in price accordingly.  Peridot can only be mined on the reservation by individual Native Americans or by families of Native Americans from the San Carlos Reservation.  Estimates put the San Carlos production of the world’s Peridot at 80% to 95% (Olson).
 

When I was a child, my father would often travel to San Carlos and buy my mother turquoise and peridot jewelry from local dealers.  Peridot quickly became a family favorite.  It is extremely beautiful when cut and faceted into jewelry.  There is no doubt that the brilliance of the olive green color is enhanced best by a setting of yellow gold.  Its fresh green color reminds me to this day of springtime.  It is a gem that never seems to dull or fade away in your jewelry box.  It truly stands out. 

 

Emerald-cut Peridot

                                       

Photo courtesy of R Weller/Cochise College

 

In fact, it is said that some of Cleopatra’s most prized gems were in fact peridots.  Some had previously believed that they were emeralds.  Peridots are often confused with emeralds; however their bright yellowish green hue is distinctly different from the green color of an emerald.  Ancient Romans nicknamed the peridot the ‘emerald of the evening’ because of its radiant green color that seemed to glow even in dim light.  From a chemical standpoint, peridot is actually a magnesium iron silicate.  The color intensity of the green depends on how much iron is actually present within the mineral (Gem).

Arizona is actually said to be America’s leading gem mining state.  Deposits of peridot, amethyst, and turquoise are found in abundance.  Peridot however is in a league of its own with its natural brilliance.  Peridot is a truly unique gemstone.  Anyone who enjoys fine jewelry and gemstones should definitely have peridot in their collection (Allen). 

 

                                                                                                Works Cited

Allen, Richard. "Peridot." Arizona's Gemstones. 1995. Gemland. 17 Apr 2007
     http://www.gemland.com/gemology.htm#peridot
Bernardine, Nancy. "Peridot." Unique Birthstone Jewelry. 2007. 17 Apr 2007
     http://www.bernardine.com/gemstones/peridot.htm
"Gem by Gem." 2007. International Colored Gemstone Association. 17 Apr 2007
     http://www.gemstone.org/gem-by-gem/english/peridot.html
Olson, Donald W. "Gemstones-Peridot." Peridot. 27 Jul 2005. United States Geological      Survey. 17 Apr 2007
     http://minerals.usgs.gov/minerals/pubs/commodity/gemstones/sp14-95/peridot.html