Black Tourmaline
Schorl · Mineral Specimen and Semi-Precious Gemstone
Crystal System
Trigonal system; prismatic crystal habit often forming striated, columnar crystals, though this specific specimen is a tumbled, massive pebble.
Mineral Group
Silicates (Cyclosilicate subgroup)
Chemical Formula
NaFe2+3Al6(Si6O18)(BO3)3(OH)4
Formation Process
Igneous and hydrothermal processes, crystallizing out of cooling pegmatitic magma rich in boron and water, often at high temperatures and pressures.
About This Crystal
A small, tumbled, opaque black pebble with a smooth yet slightly irregular surface. It exhibits a sub-metallic to vitreous luster on polished flat spots, with a deep jet-black coloration and micro-fractures typical of tumbled tourmaline.
Physical Characteristics
Color is solid black with a white to grey streak. It has indistinct cleavage, an uneven to subconchoidal fracture, and a specific gravity of approximately 3.0 to 3.2. Tenacity is brittle.
Optical Properties
Uniaxial negative with strong pleochroism in transparent varieties, though opaque schorl shows little to no optical transmission. Refractive index ranges from 1.620 to 1.698.
Hardness & Durability
Origin Region
Found globally with notable sources in Brazil, Madagascar, Pakistan, Afghanistan, and the United States (California and Maine). Forms primarily in pegmatites, hydrothermal veins, and metamorphic rocks.
Hardness & Durability
Mohs hardness of 7 to 7.5. It has fair to good toughness, though it can be sensitive to thermal shock due to internal fracturing.
Care & Maintenance
Safe to clean with warm soapy water. Avoid ultrasonic cleaners and harsh chemicals due to internal fractures. Store away from softer stones to prevent scratching.
Rarity & Value
Common and widely accessible. Value is very low for tumbled stones and small raw specimens, generally ranging from a few dollars to tens of dollars.
Special Characteristics
Exhibits pyroelectric and piezoelectric properties, meaning it generates an electrical charge when heated or subjected to mechanical pressure.
Lore & History
Historically used as a protective talisman against negative energies. In modern crystal healing, it is heavily associated with the Root Chakra and is believed to provide grounding, shielding, and energetic protection.