Peridoto

Peridoto is the gem-quality variety of the mineral olivine, a magnesium-iron silicate with the chemical formula (Mg,Fe)2SiO4. In nature the iron content ranges from magnesium-rich to iron-rich, producing olive-green to yellow-green colors. It crystallizes in the orthorhombic system, has a hardness of 6.5–7 on the Mohs scale, a vitreous luster, and is typically transparent to translucent. Peridoto commonly shows pleochroism, appearing in different greens when viewed from different directions.

The name peridoto derives from historical forms such as peridot and is linked to the gemstone trade; the color and rarity have made it prized since antiquity. Peridoto has featured in jewelry for thousands of years and has associations with ancient cultures, including Egyptian adornment.

Geology and occurrence: Peridot forms in mantle-derived rocks such as peridotite and in magmatic environments where magnesium-rich olivine crystallizes. Gem-quality material is found in several well-known localities worldwide, including the San Carlos Reservation in Arizona (United States), Mogok in Myanmar, the Kohistan and Baluchistan regions of Pakistan, Xinjiang in China, and the Zabargad (St. John’s) Island in Egypt. In addition to terrestrial sources, olivine crystals occur in some meteorites, though those are not typically used as gemstones.

Uses and care: Peridoto is primarily used as a gemstone in faceted and cabochon forms. It is relatively durable for jewelry but can be sensitive to rapid temperature changes and harsh chemicals; it should be cleaned with mild solutions and avoided sudden heat or impact. Typical cuts emphasize the stone’s olive-green hues and natural inclusions, which can add character to the gem.