Tourmaline
Elbaite (Tourmaline Group) · Semi-Precious Gemstone
Crystal System
Trigonal system, typically forming prismatic crystals with striated faces and a rounded triangular cross-section.
Mineral Group
Silicates, specifically Cyclosilicates.
Chemical Formula
Na(Al1.5Li1.5)Al6(Si6O18)(BO3)3(OH,F)4
Formation Process
Pegmatitic and hydrothermal formation, crystallizing from cooling magma rich in water, boron, and lithium at high temperatures and moderate pressures.
About This Crystal
An oval mixed-cut dark green tourmaline gemstone set in an ornate vintage-style sterling silver ring. The stone exhibits deep forest green body color with bright emerald and lime green flashes reflecting light from its faceted surface.
Physical Characteristics
Color ranges from dark green to black with vitreous luster, white streak, indistinct cleavage, uneven to conchoidal fracture, specific gravity of approximately 3.00 to 3.25, and brittle tenacity.
Optical Properties
Uniaxial negative with strong dichroism, showing darker colors when viewed parallel to the c-axis and lighter colors perpendicular to it. Refractive index ranges from 1.620 to 1.650 with moderate birefringence.
Hardness & Durability
Origin Region
Brazil, Madagascar, Afghanistan, Nigeria, USA (California and Maine); found mainly in pegmatites and hydrothermal veins.
Hardness & Durability
Mohs hardness of 7 to 7.5, fair to good durability for everyday jewelry wear, though care should be taken with sharp impacts due to lack of cleavage and brittle nature.
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic cleaners, steam cleaners, and harsh chemical treatments or sudden thermal shocks.
Rarity & Value
Common to Uncommon depending on color saturation and clarity. Fine gem-grade material with vibrant green or multi-colored zoning can command high prices. Treatments like heat treatment to lighten dark stones are occasionally used.
Special Characteristics
Strong pyroelectric and piezoelectric properties, generating an electrical charge when heated or subjected to mechanical pressure.
Lore & History
Historically associated with protection, grounding, and balancing the heart chakra. Believed in crystal lore to promote self-confidence, compassion, and emotional healing, though these are traditional beliefs rather than scientific claims.