Black Tourmaline
Schorl · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Trigonal, typically forming long, prismatic crystals with vertical striations, but presented here as a tumbled and polished stone.
Mineral Group
Silicate, specifically a Cyclosilicate belonging to the tourmaline supergroup.
Chemical Formula
NaFe2+3Al6(Si6O18)(BO3)3(OH)4
Formation Process
Primarily forms via pegmatitic and hydrothermal processes associated with cooling granitic magmas, crystallizing from boron-rich fluids at high temperatures and pressures.
About This Crystal
The specimen is a tumbled and polished stone of solid opaque black tourmaline (schorl). It has a smooth, rounded shape with a vitreous to sub-metallic luster on its polished surfaces, deep jet-black coloration, and completely opaque transparency.
Physical Characteristics
Color is solid black with a colorless or white streak. It exhibits no true cleavage (rather an indistinct conchoidal fracture), uneven to conchoidal fracture, specific gravity around 3.2 to 3.26, and is brittle with no significant magnetism.
Optical Properties
Uniaxial negative with strong pleochroism in raw crystalline forms, though not readily observable in this opaque, tumbled specimen. Refractive index ranges from approximately 1.620 to 1.655 with moderate birefringence.
Hardness & Durability
Origin Region
Worldwide, with notable deposits in Brazil, Pakistan, Madagascar, the United States (California and Maine), and Russia. Forms in pegmatites, hydrothermal veins, and metamorphic rocks.
Hardness & Durability
Mohs hardness of 7 to 7.5. It has fair toughness and good wearability for jewelry, though it can be sensitive to severe thermal shock.
Care & Maintenance
Safe to clean with warm soapy water. Avoid harsh chemical cleaners and sudden extreme temperature changes. Store separately to prevent scratching softer stones.
Rarity & Value
Common and widely available. Value is generally low to moderate, determined by the size and quality of the polished piece or crystal specimen. Treatments are rarely needed or performed.
Special Characteristics
Schorl exhibits strong pyroelectric and piezoelectric properties, generating an electrical charge when heated or subjected to mechanical pressure.
Lore & History
Historically used as a protective amulet against negative energies and psychic attacks. In modern metaphysical practices, it is heavily associated with the Root Chakra, grounding, and energetic protection, though these are traditional beliefs rather than scientific claims.