Black Tourmaline
Schorl · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Trigonal, typically forming prismatic crystals with vertical striations, but presented here as a tumbled and polished smooth pebble.
Mineral Group
Silicates, specifically the cyclosilicate subgroup.
Chemical Formula
NaFe2+3Al6(Si6O18)(BO3)3(OH)4
Formation Process
Forms primarily through pegmatitic and hydrothermal processes, crystallizing from cooling magma rich in water and boron, often at high temperatures and pressures.
About This Crystal
A smooth, tumbled, and polished dark black stone with a sub-vitreous to greasy luster. It is completely opaque with a deep, solid black coloration, showing subtle surface reflections from its tumbled finish.
Physical Characteristics
Color is deep 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 double refraction. It is strongly pleochroic in thick sections, though opaque in this specimen.
Hardness & Durability
Origin Region
Found worldwide with notable deposits in Brazil, Pakistan, Madagascar, Afghanistan, and the United States (California and Maine). It forms in pegmatites and hydrothermal veins.
Hardness & Durability
Mohs hardness of 7 to 7.5. It has good durability and is suitable for everyday jewelry wear, though care must be taken against hard impacts due to its brittleness.
Care & Maintenance
Can be safely cleaned with warm soapy water and a soft cloth. Avoid harsh chemical cleaners and ultrasonic cleaners. Store away from softer stones to prevent scratching.
Rarity & Value
Common and widely accessible. Prices for tumbled stones like this are generally very affordable, ranging from inexpensive to moderate depending on size.
Special Characteristics
Exhibits pyroelectricity and piezoelectricity, meaning it can generate an electrical charge when heated or subjected to mechanical pressure.
Lore & History
Historically used as an amulet for protection against negative energies and psychic attacks. In modern crystal healing, it is heavily associated with the Root Chakra and is believed to provide grounding, protection, and purification (traditional beliefs, not scientific claims).