mineral
Black Tourmaline (Schorl)
NaFe2+3Al6(BO3)3Si6O18(OH)4 (Schorl)
Mohs hardness 7-7.5, opaque black color, vitreous to resinous luster, trigonal crystal system, indistinct cleavage, uneven to conchoidal fracture.
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Physical properties
Mohs hardness 7-7.5, opaque black color, vitreous to resinous luster, trigonal crystal system, indistinct cleavage, uneven to conchoidal fracture.
Formation & geological history
Forms primarily in granitic pegmatites, metamorphic rocks (gneiss and schist), and high-temperature hydrothermal veins during late-stage magmatic crystallization.
Uses & applications
Widely used in lapidary arts, jewelry, gemstone collecting, and metaphysical/crystal healing practices as a protective stone. Historically used in scientific instruments for its piezoelectric properties.
Geological facts
Black tourmaline, or Schorl, is pyroelectric and piezoelectric, meaning it can generate an electrical charge when heated, cooled, or subjected to mechanical pressure. It accounts for about 95% of all natural tourmaline in the world.
Field identification & locations
Identified in the field by its deep black color, high hardness (scratches glass easily), and characteristic vertical striations along prismatic crystal faces. Common worldwide, with major deposits in Brazil, Madagascar, Pakistan, and the USA.
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