Black Tourmaline
Schorl · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Trigonal; typically forms prismatic crystals with vertical striations, but is shown here as a tumbled, massive stone.
Mineral Group
Silicates, specifically the Cyclosilicate subgroup.
Chemical Formula
NaFe2+3Al6(Si6O18)(BO3)3(OH)4
Formation Process
Primarily forms via magmatic and hydrothermal processes in granitic pegmatites and veins at high temperatures and pressures.
About This Crystal
A dark, opaque, tumbled black stone with a sub-vitreous to resinous luster. It has a smooth, polished surface characteristic of a tumbled mineral specimen, showing mottled dark grey and pitch-black color variations.
Physical Characteristics
Color is deep black, streak is white, cleavage is indistinct, 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
Singly or doubly refractive with uniaxial negative optic sign, high birefringence, and strong pleochroism in thicker translucent sections.
Hardness & Durability
Origin Region
Found globally with notable sources in Brazil, Pakistan, Madagascar, Afghanistan, and the United States (California and Maine). Forms in pegmatites, hydrothermal veins, and metamorphic rocks.
Hardness & Durability
Mohs hardness of 7 to 7.5, making it quite durable for everyday wear and handling, though it can be brittle due to internal fractures.
Care & Maintenance
Safe to clean with warm soapy water. Avoid harsh chemical cleaners and ultrasonic cleaners if the stone contains fractures. Store separately from softer gems to prevent scratching.
Rarity & Value
Common and widely available. Value is generally low for tumbled stones, ranging from inexpensive to moderate depending on size and polish quality. Treatments are rare as the material is naturally abundant.
Special Characteristics
Exhibits strong pyroelectricity and piezoelectricity, generating an electrical charge when heated or subjected to mechanical pressure.
Lore & History
Historically used as an amulet for protection against negative energies and environmental pollutants. In modern crystal healing, it is heavily associated with the Root Chakra and is believed to provide grounding and energetic shielding, though these are traditional beliefs rather than scientific claims.