Peridot is the gem variety of the mineral olivine, recognizable by its characteristic yellow-green to olive-green hue. This gemstone holds a unique distinction in the world of jewelry because, alongside diamond, it is one of the very few gems not formed within the Earth’s crust. Its attractive color is naturally derived from the iron present in its chemical structure, a magnesium iron silicate with the formula (Mg,Fe)₂SiO₄.
The Mantle and Volcanic Origins of Peridot
Peridot formation is linked to the immense pressures and temperatures found deep within the Earth’s mantle, approximately 20 to 55 miles below the surface. It crystallizes in the molten rock of the upper mantle, where the elements magnesium and iron are abundant. The resulting material is a component of peridotite, a dense, coarse-grained igneous rock that constitutes the bulk of the upper mantle.
Peridot is brought to the surface primarily through two different forms of volcanic activity. The first, and most common for commercial deposits, involves the gem being embedded in basaltic lava flows, which act as a carrier bringing the olivine crystals to the surface during eruptions. The second method involves the ejection of xenoliths, fragments of mantle rock trapped in the rising magma. These xenoliths, often composed of olivine-rich dunite, are blasted out during explosive volcanic events, delivering the gem-quality peridot crystals to accessible surface locations.
Primary Commercial Sources of Peridot
Most of the world’s commercial peridot supply originates from a few distinct regions. For many years, the San Carlos Apache Reservation in Arizona, USA, has been the dominant global source, supplying an estimated 80% to 95% of the world’s production. The peridot here occurs as small, weathered-out grains and aggregates within basalt flows on Peridot Mesa. These deposits produce a vibrant, grassy green material, though the crystals are generally smaller, rarely yielding faceted stones over 10 carats.
Another major contemporary supplier is China, particularly from regions like Inner Mongolia and the Tibetan Plateau. China provides a substantial amount of calibrated, commercial-grade peridot used in jewelry. These stones tend to be lighter in color but are valued for their high volume and affordability.
Pakistan
Pakistan, particularly the mountainous regions of Kashmir and Gilgit-Baltistan, is highly regarded for producing exceptional quality peridot. The deposits in areas like Sapat Gali yield fine, large crystals with a deep green hue and high transparency. This material often commands a premium and is sought after for statement jewelry pieces.
Notable Historical and Secondary Deposits
Historically significant peridot comes from Zabargad Island (St. John’s Island), located in the Red Sea off the coast of Egypt. This island was the primary source of peridot for ancient civilizations, with mining operations dating back as far as 1500 B.C. The peridot here formed in late-stage hydrothermal veins within uplifted mantle rock, yielding historically large crystals. While historically crucial, the island’s deposits are now largely depleted, and production has been minimal for decades.
The Mogok region of Myanmar is another celebrated source, known for producing some of the world’s finest quality peridots. Burmese peridot is highly prized for its deep, rich color and excellent clarity, often yielding large cut stones. Although its output is less consistent than the primary commercial mines, the material from the Pyaunggaung area remains a benchmark for the gem’s intense color.
Minor sources include:
- The Lam Dong Province in southern Vietnam, which produces large carat crystals.
- Deposits in Norway, which are known for a light but pure green color.