Black Tourmaline
Schorl · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Trigonal, typically forming prismatic crystals with a triangular cross-section and striated faces
Mineral Group
Silicates, specifically the cyclosilicate subgroup
Chemical Formula
NaFe3Al6(Si6O18)(BO3)3(OH)4
Formation Process
Forms primarily in pegmatites, hydrothermal veins, and metamorphic rocks under high-temperature and high-pressure conditions
About This Crystal
The specimen is a tumbled, highly polished, opaque, deep black stone with a sub-metallic to vitreous luster, exhibiting minor natural surface irregularities typical of tumbled tourmaline
Physical Characteristics
Black body color with a white streak, conchoidal to uneven fracture, distinct cleavage is generally absent, specific gravity ranges from 3.0 to 3.2, and tenacity is brittle
Optical Properties
Doubly refractive with a negative optical sign, strong pleochroism from dark brown or black to lighter shades of brown, and a refractive index between 1.620 and 1.698
Hardness & Durability
Origin Region
Found globally with notable deposits in Brazil, Madagascar, Pakistan, Russia, and the United States (California, Maine)
Hardness & Durability
Mohs hardness of 7 to 7.5, fair to poor toughness due to brittleness and internal fracturing, making it moderately durable for jewelry with protective settings
Care & Maintenance
Clean with warm soapy water and a soft cloth, avoid ultrasonic and steam cleaners, store separately to prevent scratching softer stones, and protect from harsh chemicals
Rarity & Value
Common and widely available worldwide, with value determined by size, polish quality, and crystal perfection; tumbled stones are very affordable
Special Characteristics
Exhibits strong pyroelectric and piezoelectric properties, generating an electric charge when heated or subjected to mechanical pressure
Lore & History
Historically used as a protective talisman against negative energies and psychic attacks by ancient magicians; widely associated in modern crystal healing with the Root Chakra and energetic grounding