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 stone.
Mineral Group
Silicates - Cyclosilicates
Chemical Formula
NaFe3+2Al6(Si6O18)(BO3)3(OH)4
Formation Process
Igneous and hydrothermal processes, primarily crystallizing out of cooling pegmatitic magma chambers and hydrothermal veins rich in boron and water at medium to high temperatures.
About This Crystal
The specimen is a smoothly tumbled and polished pebble of deep black color. It has an opaque transparency with a vitreous to sub-metallic luster on its polished surface, showing gentle rounded contours typical of tumbling.
Physical Characteristics
Opaque jet black body color with a white streak. It has no true cleavage planes visible on this tumbled piece, exhibits a conchoidal to uneven fracture, specific gravity around 3.0 to 3.2, and is brittle in tenacity. Generally non-fluorescent.
Optical Properties
Singly or doubly refractive depending on orientation, but completely opaque in this specimen, meaning optical phenomena like birefringence and pleochroism are not visible.
Hardness & Durability
Origin Region
Worldwide, with notable deposits in Brazil, Madagascar, Pakistan, Russia, and the United States (California, Maine). Forms in pegmatites, hydrothermal veins, and metamorphic rocks.
Hardness & Durability
Mohs hardness of 7 to 7.5. Good durability, though can be brittle along internal fracture lines if dropped. Suitable for most types of jewelry if securely set.
Care & Maintenance
Safe to clean with warm soapy water and a soft brush. Avoid harsh chemical cleaners and ultrasonic cleaners if internal fractures are suspected. Store separately to avoid scratching softer stones.
Rarity & Value
Common and widely accessible. Inexpensive in its tumbled form, with value increasing for large, well-formed raw crystal specimens or matrix specimens.
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 a protective talisman against negative energies and psychic attack. In modern crystal healing, it is strongly associated with the root chakra for grounding, protection, and clearing energetic blockages. These are traditional beliefs and not scientific properties.