Black Tourmaline
Schorl · Mineral Specimen and Semi-Precious Gemstone
Crystal System
Trigonal, prismatic habit with characteristic vertical striations
Mineral Group
Silicates, specifically the Cyclosilicate subgroup
Chemical Formula
NaFe2+3Al6(Si6O18)(BO3)3(OH)4
Formation Process
Igneous and hydrothermal processes, commonly crystallizing in granite pegmatites, hydrothermal veins, and metamorphic rocks
About This Crystal
Opaque black prismatic crystal column with prominent vertical striations along the length, vitreous to resinous luster on fresh surfaces, and a somewhat fibrous or splintery termination
Physical Characteristics
Deep black body color, colorless streak, no true cleavage but distinct parting, uneven to conchoidal fracture, specific gravity around 3.0 to 3.2, brittle tenacity, and piezoelectric and pyroelectric properties
Optical Properties
Uniaxial negative with strong pleochroism, refractive index ranging from 1.620 to 1.650, birefringence of 0.018 to 0.040, opaque in this massive black variety
Hardness & Durability
Origin Region
Brazil, Pakistan, Madagascar, USA (California, Maine), and various pegmatite-rich regions worldwide
Hardness & Durability
Mohs hardness of 7 to 7.5, fair to poor toughness due to brittleness, stable under normal environmental conditions
Care & Maintenance
Clean with warm soapy water and a soft brush, avoid harsh chemicals, ultrasonic cleaners, and extreme thermal shock, store wrapped separately to prevent scratching softer stones
Rarity & Value
Common, widely available worldwide as mineral specimens, highly affordable unless part of exceptionally large or aesthetic matrix displays
Special Characteristics
Strong pyroelectric and piezoelectric properties, generating an electrical charge when heated or subjected to mechanical pressure
Lore & History
Historically used as an amulet for protection against negative energies and environmental pollutants, heavily utilized in modern crystal healing for root chakra grounding and shielding