Black Tourmaline
Schorl · Semi-Precious Gemstone and Mineral Specimen.
Crystal System
Trigonal, typically forming prismatic crystals with a striated triangular cross-section, though this specimen is tumbled into a smooth, rounded pebble shape.
Mineral Group
Silicates, specifically the Cyclosilicate subgroup.
Chemical Formula
NaFe2+3Al6(Si6O18)(BO3)3(OH)4
Formation Process
Primarily forms via pegmatitic and hydrothermal processes associated with cooling magma chambers, as well as in metamorphic environments under high temperatures and pressures.
About This Crystal
The specimen is a smoothly tumbled, polished black stone with a sub-metallic to vitreous luster. It is opaque with a deep, solid black color throughout, displaying minor surface reflections from the polishing process.
Physical Characteristics
Color is solid black with a white streak. It has no distinct cleavage, exhibits an uneven to conchoidal fracture, has a specific gravity of approximately 3.0 to 3.2, and is brittle in tenacity.
Optical Properties
Uniaxial negative with a refractive index ranging from 1.620 to 1.698. It shows strong pleochroism in rough crystal form, though absent in this opaque tumbled piece.
Hardness & Durability
Origin Region
Found worldwide including Brazil, Pakistan, Madagascar, the United States, and Russia. It typically forms in pegmatites, hydrothermal veins, and metamorphic rocks.
Hardness & Durability
Mohs hardness of 7 to 7.5. It has good durability and wearability for jewelry, lacking easy cleavage planes, making it resistant to standard impacts.
Care & Maintenance
Safe to clean with warm soapy water. Avoid harsh chemical cleaners and prolonged exposure to extreme heat, though it does not fade easily in sunlight.
Rarity & Value
Very common and widely accessible. Prices for tumbled stones like this are generally very affordable, usually ranging from a few dollars upwards depending on size.
Special Characteristics
Schorl exhibits pyroelectric and piezoelectric properties, meaning it can generate 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 is believed to provide grounding, protection, and purification.