Fig. 1. Rachel Fero. Olivine Pools. July 2004
Last summer, my aunt and uncle brought me on a trip to
pronounced peridoe, is the gem variety of olivine, has the hardness of 6.5 to 7
and has poor cleavage in two directions at 90 degrees. It breaks in conchoidal fractures. Peridot is a magnesium-iron rich silicate
mineral. Its chemical formula is
(MgFe)2SiO4. The scientific name for
peridot is Magnesium Iron Silicate.
There are two minerals in the same family that are similar to peridot,
fayalite and forsterite. Fayalite,
Fe2SiO4, is rich in iron and forsterite, Mg2SiO4, is rich in magnesium. Because of its iron content, fayalite is
usually slightly darker and heavier than forsterite and peridot but they are
hard to tell apart. Since they are hard
to tell apart, they are all usually called olivine. “The best colored peridot has an iron
percentage less than 15% and includes nickel and chromium as trace elements
that may also contribute to the best peridot color” (Olivine). The color of peridot ranges from light
emerald green to pale yellowish green, which is the most common color. Peridot can also be clear and greenish brown
to black. Olivine can be transparent or
translucent and has a vitreous luster.
Peridot forms as grains inside basalt. After the basalt weathers, the peridot appears and can be easily found. If you don’t want to wait for weathering, drilling and blasting is required. The most common size of peridot that is found is about one carat but larger sizes can be found. Flawless stones five carats and over are rare.
Peridot has been
a favorite gemstone for jewelry for a long time. Some people believe the emeralds Cleopatra
wore were not emeralds, but peridot instead.
“Peridot is the birthstone
of August and is usually a very affordable colored gemstone. Unfortunately it is often compared to the
rich dark green of emerald and in this comparison it is often found lacking. But peridot has its own unique green-yellow
color that is different from emerald and this comparison is rather unfair”
Peridot is often worn because it is
supposed to bring success, peace, and good luck. It can be tumbled and set in baroque jewelry
or even made into beads. Peridot can
also be used in mosaics but the most popular way to display peridot is faceted
and set in rings, earrings, bracelets and in many other types of jewelry. Olivine also has industrial uses such as
refractory sands and abrasives.
Amethyst Galleries Inc. Olivine (Magnesium
Iron Silicate). 2002. 9 April 2005. http://mineral.galleries.com/minerals/silicate/olivine/olivine.htm
Doughty, Andrew, and Harriet Friedman.
Fero, Rachel. Olivine Pools Picture. July 2004.
United States Geological Survey. Gemstones-Peridot. 17 July 2002. 9 April 2005. http://minerals.usgs.gov/minerals/pubs/commodity/gemstones/sp14-95/peridot.html