Black Tourmaline
Schorl · Mineral Specimen and Semi-Precious Gemstone.
Crystal System
Trigonal system with typically prismatic crystal habit and vertical striations.
Mineral Group
Silicates, specifically Cyclosilicates.
Chemical Formula
NaFe2+3Al6(Si6O18)(BO3)3(OH)4
Formation Process
Primarily forms through pegmatitic and hydrothermal processes at high temperatures and pressures associated with granitic magma intrusion.
About This Crystal
The specimen is shaped into a polished tower or wand with a hexagonal cross-section and a pointed pyramidal top. It has an opaque, solid black color with a highly reflective, vitreous to sub-metallic luster on its polished facets.
Physical Characteristics
Body color is solid black, streak is white, cleavage is indistinct, fracture is uneven to conchoidal, specific gravity is approximately 3.0 to 3.2, and tenacity is brittle.
Optical Properties
Uniaxial negative with strong pleochroism in thick sections, though opaque in this specimen; refractive index ranges from 1.620 to 1.650.
Hardness & Durability
Origin Region
Notable sources include Brazil, Madagascar, Pakistan, Afghanistan, and the United States (California, Maine). It typically forms in pegmatites and hydrothermal veins.
Hardness & Durability
Mohs hardness of 7 to 7.5, making it relatively durable for jewelry use, though its brittle tenacity and potential for internal fractures require care.
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid harsh chemical cleaners and ultrasonic cleaners due to potential internal fractures. Store separately to prevent scratching softer stones.
Rarity & Value
Common and widely available worldwide. Value depends on size, perfection of natural crystal form, and absence of cracks. Usually affordable, ranging from a few dollars to moderate prices for large polished towers.
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 various cultures. In modern crystal healing, it is strongly associated with the Root Chakra and believed to provide grounding and energetic protection.