Peridot is the gem-quality form of the mineral olivine, and it holds a unique place among gems: it is idiochromatic, meaning its color is part of the mineral's essential chemistry rather than a trace impurity. The iron that builds every olivine crystal also colors it, so peridot is always green and comes in essentially one hue, a warm yellowish green found in no other gem.
A color you cannot mistake
Peridot ranges from yellowish green to a pure, grassy green, with the finest stones a rich green at around 10 carats and above. Because the color is intrinsic, there is no "colorless peridot" and no blue or red version; the variation is only in how yellow or how pure the green appears. The most valued tone is a lively green with as little brown or excess yellow as possible.
Strong doubling and good brilliance
Peridot has notably high double refraction: look through a faceted stone with a loupe and you can often see the back facets appear doubled. This gives peridot a soft, velvety richness and is a handy identification clue. Its refractive index and luster give it a lively, slightly oily brilliance.
From volcanoes, and from space
Most peridot forms deep in the Earth's mantle and is carried up by volcanoes; the famous San Carlos deposit in Arizona is a major source, along with Pakistan (fine large crystals from Kohistan) and Myanmar. Historically the finest came from Zabargad Island in Egypt's Red Sea, mined for thousands of years. Peridot has even been found in pallasite meteorites, making it one of the few gems with an extraterrestrial pedigree.
Durable enough, with limits
At Mohs 6.5 to 7, peridot is durable enough for rings, pendants, and earrings, but it sits just below the dust-resistant threshold and is more brittle than quartz. It is also sensitive to acids (even sweat over long periods) and to sudden temperature shocks, which can fracture it. It suits everyday wear best in protective settings and benefits from occasional care.
Untreated by nature
Peridot is one of the gems that is usually not treated. Occasionally fractured stones are filled to improve clarity, but standard peridot is natural color and clarity, which makes it refreshingly straightforward to buy. Synthetic peridot exists but is uncommon in jewelry.
Caring for peridot
Clean peridot with warm soapy water and a soft cloth, never harsh chemicals or acids. Avoid ultrasonic and steam cleaners, which can crack it, and take rings off before strenuous work. Store it away from harder gems so its surface stays bright.
Peridot is proof that one color can be enough. Its built-in green needs no treatment, its meteorite history gives it romance, and with gentle care this ancient "gem of the sun" wears beautifully for a lifetime.
