Peridot (Olivine)

Hardness: 6-7 on Mohs scale. Color: Greenish-yellow, olive green, brown-green, sometimes with a golden sheen. Luster: Vitreous to greasy. Crystal Structure: Orthorhombic. Cleavage: Poor in one direction. Specific Gravity: 3.2-4.4. Streak: White.

Peridot crystallizes at high temperatures from magnesium-rich and iron-rich magma. It is typically found in mafic and ultramafic igneous rocks such as basalt, peridotite, and dunite. It can also be found in some metamorphic rocks, although less commonly. Its formation process is primarily magmatic, often brought to the Earth's surface during volcanic activity. Geological age varies depending on the specific deposit, but it is common in rocks from various geological eras.

Peridot is primarily used as a gemstone in jewelry, especially as a birthstone for August. Larger, high-quality specimens are highly valued. Industrially, olivine (the mineral group to which peridot belongs) is used as a refractory material, as a sandblasting abrasive, and in the production of magnesium. It also has potential uses in carbon capture and sequestration due to its ability to react with CO2.

Peridot is the gem-quality variety of olivine and is one of the few gemstones that occurs in only one color: green. Its green color is due to the presence of iron in its crystal structure. Peridot has been found in meteorites and is sometimes called 'space gem.' It was historically known as the 'gem of the sun' by ancient Egyptians.

In the field, peridot is identified by its distinctive olive-green color, its vitreous to greasy luster, and its often rounded habit when found in weathered volcanic rocks. It has a high specific gravity and typically appears as small crystals. Common locations include the San Carlos Apache Reservation in Arizona (USA), which is a major source; other notable localities are Myanmar, Pakistan, China, Vietnam, and Norway. For collectors, look for well-formed crystals in basaltic rocks or as loose alluvial grains. Its unique green hue helps distinguish it from other green minerals.