Black Tourmaline
Schorl · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Trigonal, typically forming prismatic crystals with striated faces, but seen here as polished spherical beads.
Mineral Group
Silicates, specifically the Cyclosilicate subgroup.
Chemical Formula
NaFe3Al6(Si6O18)(BO33)(OH)4
Formation Process
Forms primarily through pegmatitic and hydrothermal processes where boron-rich fluids interact with surrounding rocks at high temperatures and pressures.
About This Crystal
The specimen consists of polished, opaque spherical beads showcasing a deep black body color with a vitreous to sub-metallic luster. The surface is smooth and reflective due to polishing, lacking visible natural crystal faces.
Physical Characteristics
Opaque black color, white to grey streak, no distinct cleavage planes visible due to bead form, conchoidal to uneven fracture, specific gravity around 3.0 to 3.2, brittle tenacity, non-magnetic, and generally inert under UV light.
Optical Properties
Doubly refractive with uniaxial negative optical sign, strong pleochroism in natural rough form (darker colors along the c-axis), but optical effects are largely obscured by opacity in polished bead form.
Hardness & Durability
Origin Region
Found globally with notable sources in Brazil, Madagascar, Pakistan, Sri Lanka, and the United States (Maine and California). It forms in pegmatites, hydrothermal veins, and metamorphic rocks.
Hardness & Durability
Mohs hardness of 7 to 7.5, making it quite durable and suitable for daily jewelry wear like bracelets, though it has distinct brittleness and can fracture under sharp impacts.
Care & Maintenance
Clean with warm soapy water and a soft cloth. Avoid ultrasonic and steam cleaners. Store away from harder gemstones to prevent scratching and keep protected from prolonged harsh chemicals.
Rarity & Value
Common and widely accessible. Value is generally low to moderate, depending on the uniformity and quality of the bead polish, making it very popular for bead bracelets and carvings.
Special Characteristics
Exhibits strong pyroelectric and piezoelectric properties, meaning it can generate an electrical charge when heated or subjected to mechanical pressure.
Lore & History
Historically used as a protective talisman against negative energies and psychic attack. In modern crystal healing, it is heavily associated with the root chakra for grounding, protection, and purification, though these remain traditional beliefs rather than scientifically proven claims.