Black Tourmaline
Schorl · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Trigonal, typically forming prismatic crystals with striated faces
Mineral Group
Silicates, specifically the cyclosilicate subgroup
Chemical Formula
NaFe3+2Al6(Si6O18)(BO3)3(OH)4
Formation Process
Igneous and hydrothermal processes, typically crystallizing in granite pegmatites and high-temperature hydrothermal veins from boron-rich fluids.
About This Crystal
The specimen is a tumbled, polished stone of deep black color with a smooth, glossy surface and high vitereous to sub-metallic luster. It is completely opaque, showing no internal transparency, and displays a solid black body color with minor surface scuffs typical of tumbled stones.
Physical Characteristics
Black body color with a white streak, indistinct cleavage, conchoidal to uneven fracture, specific gravity around 3.0 to 3.2, brittle tenacity, non-magnetic, and exhibits strong pyroelectric and piezoelectric properties.
Optical Properties
Uniaxial negative with moderate birefringence, strong pleochroism in rough prismatic crystals (though not visible in this tumbled, opaque state), and singly or doubly refractive.
Hardness & Durability
Origin Region
Found globally with notable sources in Brazil, Pakistan, Madagascar, and the United States (California and Maine); forms primarily in pegmatites, hydrothermal veins, and metamorphic rocks.
Hardness & Durability
Mohs hardness of 7 to 7.5, making it durable for general jewelry use, though its brittleness means it can fracture under sharp impacts.
Care & Maintenance
Clean with warm soapy water and a soft cloth, avoiding harsh chemicals, ultrasonic cleaners, and steam cleaners. Store away from harder stones to prevent scratching.
Rarity & Value
Common and widely available, making tumbling rough inexpensive. Value depends on size and quality of polish, generally very affordable.
Special Characteristics
Exhibits strong piezoelectric and pyroelectric properties, generating an electrical charge when heated, cooled, or subjected to mechanical pressure.
Lore & History
Historically used as a protective talisman against negative energies and psychic attack in various cultures. In modern crystal healing, it is strongly associated with the Root Chakra and is believed to provide grounding, protection, and electromagnetic field (EMF) shielding, though these are traditional beliefs rather than scientific claims.