Peridot in Basalt (Olivine in Volcanic Rock)
Magnesium Iron Silicate (Forsterite-Fayalite series) in Mafic Igneous Vessel · Mineral Specimen / Semi-Precious Gemstone in Matrix
Crystal System
Orthorhombic; Habit is typically granular, glassy mass (phenocrysts) embedded in an aphanitic or vesicular matrix
Mineral Group
Silicates (Nesosilicate subgroup for Olivine); Silicate/Oxide mixture for Basalt
Chemical Formula
(Mg, Fe)2SiO4 (Olivine) with Al, Ca, Na, K, P, Ti, Cr contained in the surrounding Basalt matrix
Formation Process
Igneous: Forms deep in the Earth's mantle and is carried to the surface by basaltic magma during volcanic eruptions. Crystallization occurs under high pressure and temperature.
About This Crystal
Granular, translucent lime-green to olive-yellow crystals (Olivine) embedded in a dark grey to charcoal, opaque, often vesicular (pitted) volcanic rock known as basalt. The luster of the crystals is vitreous (glassy), while the matrix is dull to earthy.
Physical Characteristics
Color: Green to yellow-green crystals, dark grey matrix. Streak: White to colorless. Cleavage: Poor in olivine. Fracture: Conchoidal (olivine), uneven (basalt). Specific Gravity: 3.2-4.3 (olivine). Non-fluorescent under UV light.
Optical Properties
Refractive Index: 1.635-1.690 (Olivine); Birefringence: 0.035-0.038; Doubly refractive. Pleochroism: Weak (yellow-green to green). Matrix is non-optical/opaque.
Hardness & Durability
Origin Region
Notable sources include Peridot Mesa, Arizona (San Carlos Apache Reservation), Hawaii, and Canary Islands (Spain). Typically found in volcanic fields.
Hardness & Durability
Mohs Hardness: 6.5 to 7 for the Olivine crystals. Matrix is variable but generally 5-6. Brittle tenacity; susceptible to thermal shock.
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic and steam cleaners. Protect from abrupt temperature changes and acids. Store separately to prevent matrix from scratching or being scratched.
Rarity & Value
Common as a geological specimen, but gem-quality crystals over 1ct in the matrix are uncommon. Values range from $10 to $100+ depending on crystal size and matrix aesthetic. Unlikely to be treated in this raw form.
Special Characteristics
Features distinct phenocrysts (individual crystals) in an aphanitic matrix. Some specimens may show vesicular textures (bubbles) in the basalt from escaping gas during cooling.
Lore & History
Historically, Peridot was used as a talisman to ward off 'evil spirits' in ancient Egypt. In metaphysical lore, it is associated with the Heart Chakra, believed to promote compassion and emotional balance. Basalt is viewed as a grounding stone from the Earth's core.