Black Tourmaline
Schorl · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Trigonal crystal system, typically forming prismatic crystals with a triangular cross-section and striated vertical faces, here tumbled into a smooth, rounded pebble shape.
Mineral Group
Silicates, specifically the cyclosilicate subgroup within the tourmaline supergroup.
Chemical Formula
NaFe2+3Al6(Si6O18)(BO3)3(OH)4
Formation Process
Primarily forms in pegmatites and hydrothermal veins through the crystallization of boron-rich silicate melts and hot aqueous fluids at high temperatures and pressures.
About This Crystal
A tumbled, polished specimen of deep black color with a sub-vitreous to resinous luster. The surface is smooth and rounded from tumbling, with some natural internal fractures, pitting, and lighter whitish or greyish inclusions visible near the center.
Physical Characteristics
Color is opaque black with a white streak. It has no true cleavage, instead exhibiting uneven to conchoidal fracture. Specific gravity ranges from 3.0 to 3.2. Tenacity is brittle, and it does not exhibit significant fluorescence under UV light.
Optical Properties
Uniaxial negative with moderate birefringence. Displays strong pleochroism in rough crystalline form, though difficult to observe in opaque, tumbled black specimens. It is doubly refractive.
Hardness & Durability
Origin Region
Found globally with notable sources in Brazil, Pakistan, Afghanistan, Africa (Madagascar, Namibia), and the USA (California, Maine). Forms primarily in granitic pegmatites, hydrothermal veins, and metamorphic rocks.
Hardness & Durability
Mohs hardness of 7 to 7.5, making it quite durable and suitable for general jewelry use, though poor cleavage planes in raw crystals can make them sensitive to sharp impacts.
Care & Maintenance
Can be cleaned safely with warm soapy water and a soft brush. Avoid harsh chemical cleaners and ultrasonic cleaners due to internal fractures. Store separately from softer stones to prevent scratching.
Rarity & Value
Common and widely available. Value is very affordable, primarily determined by size, polish quality, and absence of excessive surface pitting. Treatments are rare since 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 magicians and shamans to ward off negative energies and psychic attack. In modern crystal healing, it is heavily associated with the Root Chakra, grounding, energetic protection, and EMF shielding.