Peridot (Olivine)

Hardness: 6.5-7 on Mohs scale. Color: Olive-green, yellowish-green to brownish-green. Luster: Vitreous (glassy) to oily. Crystal Structure: Orthorhombic. Cleavage: Poor in two directions. Specific Gravity: 3.27-3.37. Often transparent to translucent, and can exhibit a 'sleepy' appearance due to internal inclusions.

Peridot is the gem-quality variety of the mineral Olivine. It forms in mafic and ultramafic igneous rocks such as basalt and peridotite, deep within the Earth's mantle, and is brought to the surface by volcanic activity. It can also be found in certain types of meteorites (pallasites). Its formation involves crystallization from magnesium and iron-rich molten rock. Geological Age: Varies widely depending on the volcanic activity, but Olivine is a primitive mineral, often found in some of the Earth's oldest rocks, and in relatively young volcanic rocks.

Peridot is primarily used as a gemstone in jewelry. Its vibrant green color makes it popular for rings, necklaces, earrings, and bracelets. Due to its relative abundance and attractive color, it is an affordable alternative to more expensive green gemstones like emerald. Historically, large deposits of peridot were known for their use in royal jewelry.

Peridot obtains its green color from the presence of iron in its chemical structure; the intensity of the green depends on the amount of iron present. It is one of the few gemstones that occurs in only one color. Peridot found in meteorites is extraterrestrial in origin. The largest faceted peridot is 310 carats and is located at the Smithsonian National Museum of Natural History. In ancient times, it was called 'the gem of the sun' and believed to ward off evil spirits.

To identify peridot in the field, look for its distinctive olive-green color and vitreous luster. It is commonly found in volcanic areas where basaltic rocks are prevalent, such as Arizona, USA; San Carlos Apache Reservation, USA (which is a primary source); Egypt (historically, on the island of St. John or Zabargad); Myanmar; Pakistan; China; and Vietnam. Inclusions such as small black chromite crystals or shiny 'lily pad' fractures can also be indicative. Collectors should look for vibrant green stones with good clarity and minimal inclusions. Its relative hardness makes it durable enough for everyday wear in jewelry.