Black Tourmaline
Schorl · Mineral Specimen and Semi-Precious Stone
Crystal System
Trigonal system, typically forming prismatic crystals with striated faces, often massive or columnar in habit.
Mineral Group
Silicates, specifically the cyclosilicate subgroup.
Chemical Formula
NaFe2+3Al6(Si6O18)(BO33)(OH)4
Formation Process
Primarily forms via pegmatitic and hydrothermal processes associated with cooling granitic magmas, as well as in regional metamorphic environments at high temperatures and pressures.
About This Crystal
The specimen is a small, dark, opaque, rough mineral fragment held in the palm of a hand. It exhibits a sub-metallic to vitreous luster with uneven, textured surfaces reflecting light from micro-crystalline facets or fractured areas.
Physical Characteristics
Color is deep black with a white streak. It has no true cleavage, breaking with an uneven to conchoidal fracture. Specific gravity is approximately 3.0 to 3.2. Tenacity is brittle.
Optical Properties
Uniaxial negative with strong pleochroism in transparent varieties, though this specimen is opaque and exhibits no transmitted optical phenomena.
Hardness & Durability
Origin Region
Found globally with notable sources in Brazil, Pakistan, Afghanistan, Madagascar, and the USA (California and Maine). Forms in pegmatites, hydrothermal veins, and metamorphic rocks.
Hardness & Durability
Mohs hardness of 7 to 7.5. It has fair toughness and is reasonably durable for wear, though brittle under sharp impacts.
Care & Maintenance
Safe to clean with warm soapy water. Avoid ultrasonic cleaners and harsh chemicals. Store separately from softer stones to prevent scratching.
Rarity & Value
Common and widely accessible. Value depends on specimen aesthetics, crystal size, and completeness, typically ranging from inexpensive raw pieces to moderate prices for fine crystal clusters.
Special Characteristics
Displays strong pyroelectric and piezoelectric properties, generating an electrical charge when heated or subjected to mechanical pressure.
Lore & History
Historically used as a protective talisman against negative energies and psychic attack. In modern crystal healing, it is associated with the root chakra and believed to provide grounding and energetic shielding.