Peridot is the birthstone for August and the 15th anniversary gemstone.
Found in lava, meteorites, and deep in the earth’s mantle, yellow-green peridot is the extreme gem.
The word peridot comes from the Arabic “faridat,” which means “gem.” Most peridot formed deep inside the earth and was delivered to the surface by volcanoes. Some also came to earth in meteorites, but this extraterrestrial peridot is extremely rare, and not likely to be seen in a retail jewelry store.
Gem miners find peridot as irregular nodules (rounded rocks with peridot crystals inside) in some lava flows in the United States, China, and Vietnam and, very rarely, as large crystals lining veins or pockets in certain types of solidified molten rock. Geologists believe these deposits relate to the spreading of the sea floor that occurs when the earth’s crust splits, and rocks from its mantle are pushed up to the surface. Sometimes these rocks can be altered, deformed, and incorporated into mountain ranges by later earth movements.
Peridot color ranges from a brown-green color to yellowish green to pure green. Yellowish green is the most common peridot color seen in jewelry.
Peridot is the gem variety of the mineral olivine. Its chemical composition includes iron and magnesium, and iron is the cause of its attractive yellowish green colors. The gem often occurs in volcanic rocks called basalts, which are rich in these two elements.
Color Although the best peridot is a pure grass green, most peridot is yellowish-green. The pure grass green color, is usually only achieved in gems of 10-cts. or larger. Smaller examples tend to show yellowish-green hues and brown undertones lower the value of peridot.
Clarity The best-quality peridot has no eye-visible inclusions, with perhaps a few tiny black spots visible under magnification. Other inclusions common in peridot are reflective, disk-shaped inclusions called “lily pads.”
Cut Peridot can be a stunning gem with skilled cutting to maximize its beautiful color. It’s available in a wide variety of shapes and cutting styles, including ovals, pears, rounds, emerald cuts, cushion cuts, triangle cuts, and marquise shapes.
Carat Weight Although the finest gems are generally seen in sizes above 10-cts. and there are fine gems of more than 50-cts. on the market, smaller gems cut to standard sizes are affordable and readily available.
Caring for your peridot
- Durability Peridot is durable enough for jewelry wear but should be worn with some care so as not to scratch it.
- CARE AND CLEANING Warm soapy water is always safe.
- TREATMENT Peridot is rarely treated, but might have fractures. Only clean fracture-filled gemstones with warm, soapy water.
- MINERAL: Olivine
- CHEMISTRY: (MgFe)2SiO4
- COLOR: Yellowish green
- REFRACTIVE INDEX: 1.65 to 1.69
- BIREFRINGENCE: 0.035 to 0.038
- SPECIFIC GRAVITY: 3.34
- MOHS HARDNESS: 6.5 to 7
“Peridot Gemstone | Peridot Stone – GIA.” Peridot Gemstone | Peridot Stone – GIA. N.p., n.d. Web. 27 July 2016.