Peridot (Olivine in Basalt)
Olivine var. Peridot · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Orthorhombic; typically occurs as rounded grains or stubby prismatic crystals in volcanic matrix.
Mineral Group
Silicates; Subgroup: Nesosilicates
Chemical Formula
(Mg, Fe)2SiO4
Formation Process
Igneous/Magmatic; forms deep in the Earth's mantle and is carried to the surface by basaltic magmas during volcanic eruptions.
About This Crystal
Small, olive-green to lime-green transparent to translucent grains embedded in a dark, porous basaltic matrix. Exhibits a vitreous (glassy) luster and typical granular habit.
Physical Characteristics
Color: Olive-green; Streak: White; Cleavage: Poor/Imperfect; Fracture: Conchoidal; Specific Gravity: 3.27–3.37; Fluorescence: Generally none.
Optical Properties
Biaxial positive; Refractive Index: 1.654–1.690; Birefringence: 0.035–0.038; Strong doubling of back facets often visible in cut stones.
Hardness & Durability
Origin Region
Notable sources include San Carlos Apache Reservation (Arizona, USA), Pakistan, Myanmar, and Lanzarote (Canary Islands).
Hardness & Durability
Mohs Hardness: 6.5–7.0; Brittle tenacity; sensitive to rapid temperature changes and strong acids.
Care & Maintenance
Clean with warm soapy water only; avoid ultrasonic and steam cleaners. Store away from harder stones like sapphire or diamond to prevent scratching.
Rarity & Value
Common in small granular form; gem-quality crystals over 10 carats are rare. Value is driven by 'grass-green' saturation and clarity.
Special Characteristics
Contains 'lily pad' inclusions (discoid tension fractures) in faceted gems; idiochromatic (colored by its basic chemical composition, iron).
Lore & History
Known as the 'Gem of the Sun' in Ancient Egypt. Historically found on the island of Topazos in the Red Sea. Associated with the Heart Chakra and believed to foster abundance and emotional healing.