Black Tourmaline
Schorl · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Trigonal, typically occurring as prismatic crystals with vertical striations, but presented here as a tumbled and polished stone.
Mineral Group
Silicates, specifically the Cyclosilicate subgroup.
Chemical Formula
NaFe2+3Al6(Si6O18)(BO3)3(OH)4
Formation Process
Primarily forms via pegmatitic and hydrothermal processes at high temperatures and pressures, crystallizing from boron-rich fluids interacting with surrounding rock formations.
About This Crystal
This is a tumbled, polished specimen of deep black color with a smooth, glossy, vitreous to sub-metallic luster. The stone is opaque, displaying a rounded, irregular triangular or elongated shape typical of tumbled schorl, with minor surface imperfections preserved from the tumbling process.
Physical Characteristics
Opaque black body color with a white to greyish streak. It lacks true cleavage, instead exhibiting an uneven to conchoidal fracture. Specific gravity ranges from 3.0 to 3.2. It is brittle in tenacity and can be pyroelectric and piezoelectric.
Optical Properties
Singly or doubly refractive (uniaxial negative), with a refractive index between 1.625 and 1.699. It shows strong pleochroism in raw crystal form, shifting from dark brown/black to lighter tones, though less apparent in polished tumbled pieces.
Hardness & Durability
Origin Region
Worldwide distribution with notable deposits in Brazil, Madagascar, Pakistan, Russia, 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 and suitable for general jewelry use. It has fair toughness, but can fracture along internal stress fractures if struck hard.
Care & Maintenance
Can be safely cleaned with warm, soapy water and a soft brush. Avoid harsh chemical cleaners, prolonged exposure to extreme heat, and ultrasonic cleaners which can exacerbate internal fractures.
Rarity & Value
Common and widely accessible. Value is very low for tumbled stones and common mineral specimens, though large, pristine crystal clusters can command higher prices among collectors. Treatments are virtually nonexistent due to its abundance.
Special Characteristics
Exhibits strong pyroelectric and piezoelectric properties, generating an electrical charge when heated or subjected to mechanical pressure. Often investigated for weak magnetic attraction due to iron content.
Lore & History
Historically used as a protective talisman by ancient civilizations to ward off negative energies and psychic attacks. In modern crystal healing, it is widely associated with the Root Chakra, grounding, protection, and transmutation of dense energies into lighter vibrations. These represent traditional cultural beliefs rather than scientific properties.