Black Tourmaline
Schorl · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Trigonal system, forming prismatic crystals with a triangular cross-section and striated faces in its natural, unpolished state.
Mineral Group
Silicates, specifically belonging to the cyclosilicate subgroup.
Chemical Formula
NaFe2+3Al6(Si6O18)(BO3)3(OH)4
Formation Process
Forms primarily through pegmatitic and hydrothermal processes, crystallizing from cooling magma rich in water, boron, and other volatiles at moderate to high temperatures and pressures.
About This Crystal
The specimen is a small, tumbled, and polished smooth stone of deep opaque black color with a sub-vitreous to greasy luster, featuring minor lighter matrix patches or inclusions on its surface.
Physical Characteristics
Opaque black body color with a white streak. It has indistinct cleavage, an uneven to conchoidal fracture, and a specific gravity of approximately 3.0 to 3.2. It is brittle and non-magnetic.
Optical Properties
Singly or doubly refractive with negative uniaxial optical character. It is generally opaque in tumbled form, though thin crystal slices can show strong pleochroism.
Hardness & Durability
Origin Region
Found globally with notable deposits in Brazil, Madagascar, Pakistan, Russia, and the United States (such as 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 wear, though lack of traditional cleavage makes it relatively tough, despite its brittle nature.
Care & Maintenance
Safe to clean with warm soapy water. Avoid harsh chemical cleaners and ultrasonic or steam cleaners if there are fractures. Store separately from softer stones to prevent scratching.
Rarity & Value
Common and widely available. Value is generally low for tumbled stones and common specimens, increasing for well-formed crystal clusters. Treatments are rare as the natural material is abundant.
Special Characteristics
Exhibits pyroelectric and piezoelectric properties, generating an electrical charge when heated or subjected to mechanical pressure.
Lore & History
Historically used as a protective talisman by ancient civilizations to ward off negative energies. In modern crystal healing, it is heavily associated with the root chakra for grounding, energetic protection, and purification, though these are traditional beliefs rather than scientific claims.