Black Tourmaline
Schorl · Mineral Specimen and Semi-Precious Stone
Crystal System
Trigonal system, typically forming prismatic crystals with striated faces, often occurring in columnar or massive habits.
Mineral Group
Silicates (Cyclosilicate subgroup)
Chemical Formula
NaFe2+3Al6(Si6O18)(BO3)3(OH)4
Formation Process
Primarily forms in igneous and metamorphic environments, specifically in granite pegmatites and hydrothermal veins through the crystallization of boron-rich fluids at high temperatures and pressures.
About This Crystal
The specimen is a dark, opaque, tumbled black stone with a vitreous to sub-metallic luster on its polished surfaces and some rough matrix areas showing brownish-black inclusions.
Physical Characteristics
Color is deep black, streak is white, cleavage is indistinct/poor, fracture is uneven to conchoidal, specific gravity is approximately 3.0 to 3.2, tenacity is brittle, and it exhibits pyroelectric and piezoelectric properties.
Optical Properties
Uniaxial negative with moderate birefringence. Pleochroism is strong in transparent varieties, though this specimen is opaque. Refractive index ranges from 1.620 to 1.698.
Hardness & Durability
Origin Region
Found worldwide, with notable deposits in Brazil, Madagascar, Pakistan, Russia, and the United States (California and Maine). It typically forms in pegmatites and hydrothermal veins.
Hardness & Durability
Mohs hardness of 7 to 7.5. It has fair to good durability for jewelry, though brittle tenacity means it can fracture upon sharp impact.
Care & Maintenance
Can be cleaned with warm soapy water and a soft brush. Avoid harsh chemicals, ultrasonic cleaners, and extreme temperature shocks. Store separately from softer stones.
Rarity & Value
Common. Widely available and affordable, with prices ranging from a few dollars for tumbled stones to moderate amounts for large, well-formed mineral specimens. Treatments are generally not necessary or common.
Special Characteristics
Exhibits strong pyroelectric and piezoelectric properties, meaning it can generate an electrical charge when heated, cooled, or subjected to mechanical pressure.
Lore & History
Historically used by ancient shamans and healers for protection against negative energies and earth radiation. In modern crystal healing, it is strongly associated with the root chakra, grounding, and psychic protection, though these are traditional beliefs rather than scientific facts.