Black Tourmaline
Schorl · Mineral Specimen and Semi-Precious Stone
Crystal System
Trigonal; typically forms prismatic crystals with vertical striations, often with a triangular cross-section, but in this specific image, it appears as a polished and tumbled cube or custom cut shape rather than a natural crystal habit.
Mineral Group
Silicates (Cyclosilicate subgroup)
Chemical Formula
NaFe2+3Al6(Si6O18)(BO3)3(OH)4
Formation Process
Primarily forms in igneous and metamorphic environments, specifically in granite pegmatites and hydrothermal veins through pneumatolytic processes at high temperatures and pressures.
About This Crystal
The specimen shown is a deep, opaque black tumbled or carved stone with a smooth, glossy surface finish, displaying rounded edges and a square or cubic form, characteristic of lapidary work rather than raw crystal habit.
Physical Characteristics
Color is solid black with a submetallic to vitreous luster when polished. Streak is white. It has no true cleavage, exhibiting uneven to conchoidal fracture. Specific gravity is approximately 3.0 to 3.2. It is brittle and exhibits pyroelectricity and piezoelectricity.
Optical Properties
Singly or doubly refractive depending on viewing angle, but opaque specimens do not show distinct refraction. It is uniaxial negative with strong pleochroism in transparent varieties, though opaque schorl shows none.
Hardness & Durability
Origin Region
Found globally with notable deposits in Brazil, Madagascar, Pakistan, Afghanistan, and the United States (California and Maine). Forms in pegmatites and hydrothermal veins.
Hardness & Durability
Mohs hardness of 7 to 7.5. It has fair toughness, but lack of cleavage makes it relatively durable, though it can fracture under sharp impacts.
Care & Maintenance
Can be cleaned safely with warm soapy water and a soft brush. Avoid harsh chemical cleaners and ultrasonic cleaners if internal fractures are present. Store separately to prevent scratching softer stones.
Rarity & Value
Common and widely available. Value is determined by size, polish quality, and form. Polished pocket stones or carved shapes are very affordable, typically ranging from a few dollars to tens of dollars.
Special Characteristics
Strong pyroelectric and piezoelectric properties, meaning it can generate an electrical charge when heated or subjected to mechanical pressure. It is also well-known for its deep opaque black color.
Lore & History
Historically used as a protective talisman against negative energies and psychic attack. In modern crystal healing, it is heavily associated with the Root Chakra, grounding, and energetic protection. These are traditional belief systems and not scientifically validated properties.