Generally it can be said, that most peridots undergo no treatment at all. They are particularly not heat-treated to enhance their colour. In some cases, peridots may be oiled or treated with natural waxes in order to fill small surface fractures and to improve the gemstone's visual allure.
Peridot, the gem variety of the mineral olivine, is known by jewellery enthusiasts for its beautiful yellowish-green to green colour. The name peridot is derived from the Arabic word "faridat", which means "gem". Due to its beautiful colour, which has already been revered by the ancient Egyptians, the peridot has often been mistaken for other green gemstones. One impressive gem that adorns the shrine of the Three Kings in Cologne has been believed to be an emerald for centuries. More recent diagnosis however have revealed that it is indeed a particularly beautiful peridot.
Peridot crystals are iron magnesium silicates. They are among the few gemstones that do not only form inside the earth's crust. Some peridots are, like diamonds, born in the magma of the upper mantle. The colour of the peridot depends on the amount of iron contained in the mineral with larger concentrations resulting in deeper green colours.
The largest producer of gem quality peridot today is the United States of America. Other sources include China, Vietnam, Pakistan, Finland and Myanmar.