Peridot

Peridot¬†belongs to the forsterite-fayalite mineral series, which is part of the olivine group. It is one of the “idiochromatic” gems, meaning its color comes from the basic chemical composition of the mineral itself, not from minor impurities, and therefore will only be found in shades of green. As a matter of fact peridot is one of the few gemstones found in only one color.

The name peridot most probably derives from the Arabic word “faridat” for gem. It’s also called chrysolith (derived from the Greek word “goldstone”) and olivine, because of its color and membership to the olivine group.
Historically the volcanic island Zabargad (St. John) in the Red Sea, east of Egypt, was the most important deposit that was exploited for 3500 years. Today’s main deposits are in Arizona, China, Vietnam and Pakistan. The Pakistani peridot in particular is very fine, and a new find in Pakistan in the mid-1990′s has made peridot available to a wider market.

Peridot colors
Peridot is one of the few gemstones, which exist only in one color. Its color agent is iron that accounts for the deep green color with that slight golden hue. Chemically Peridot is just an iron-magnesium-silicate, and the intensity of color depends on the amount of iron contained. The color as such can come in any variation from yellow-green and olive to brownish green.

Peridot is not especially hard – 6.5-7 on the Mohs scale — and tends to burst under great stress and therefore is sometimes metal-foiled. Peridot has no resistance to acids.

Color
An intense, deep green color is the favorite. The best colored peridot has an iron percentage of less than 15% and includes nickel and chromium as trace elements that may also contribute to the best peridot color.

Lighting
Peridot looks best in daylight. Its brilliant green sparkle does not change in artificial light.

Clarity
Peridot is commonly a transparent stone. Inclusions can create a cloudy nature in larger stones. Peridot cat’s eye and star peridot (showing four rays of light) are known, but a rarity.

Cut
Table and step cuts are popular. Sometimes peridot gets a brilliant cut especially if to be set in gold.

Peridot location and deposits
Historically the volcanic island Zabargad (St. John) in the Red Sea, east off Egypt, was the most important deposit that was exploited for 3500 years, abandoned for many centuries, rediscovered only around 1900 and has been completely exploited since. The most important deposits nowadays are found in Pakistan (Kashmir region and Pakistan-Afghanistan border region) and is regarded as being of the finest quality. Beautiful material is also found in upper Myanmar and Vietnam. Other deposits have been found in Australia (Queensland), Brazil (Minas Gerais), China, Kenya, Mexico, Norway (north of Bergen), South Africa, Sri Lanka, Tanzania and the United States (Arizona and Hawaii).
There are no treatments known that could enhance the quality of peridot.

World-famous Peridot
Peridot is mentioned in the Bible under the Hebrew name of “pitdah”. Peridot gems along with other gems were probably used in the fabled Breastplates of the Jewish High Priests, artifacts that have never been found. Legend has it that peridot was the favorite gemstone of Cleopatra. Crusaders brought peridot to Central Europe where it is found in many medieval churches such as the Cologne Cathedral. In the Baroque era the deep green gemstone experienced another short flourishing, before it became forgotten again.
Napoleon used peridot to assure the empress Josephine of his undying love and admiration, which, of course, happened before he had their marriage annulled.
Throughout time, peridot has been confused with many other gemstones, even emerald. Many “emeralds” of royal treasures have turned out to be peridots.
The largest cut peridot was found on the island Zabargad, weights 319ct and belongs to the Smithsonian Institution in Washington D.C.
In Russia there are some cut peridots that came out of a meteorite, which came down in eastern Siberia in 1749.

Peridot gemology
Species: olivine
Color: Yellow-green, olive-green, brownish
Chemical composition: (Mg,Fe)2SiO4 magnesium iron silicate
Crystal system: Orthorhombic; short compact prisms, vertically striated
Hardness: 6.5-7 (Mohs scale)
Specific gravity: 3.28 – 3.48
Refractive index: 1.650 -1.703
Birefringence: +0.036 to +0.038
Color of streak: White,
Absorption spectrum: 497, 495, 493, 473, 453
Fluorescence: None

The Peridot zodiac, myth & legend
In ancient believes peridot was a gift of Mother Nature to celebrate the annual creation of a new world. National leaders who publicly wore peridot were in former times thought to be gentle, fair and wise.

In Antiquity, as well as in the Middle Ages people believed that the cosmos is reflected in gemstones. Peridot is assigned to planet Saturn. The esoteric movement revived the ancient belief and the gem industry made it another marketing tool to promote certain gems.