mineral
Black Tourmaline (Schorl)
Sodium Iron Aluminum Borosilicate (NaFe2+3Al6(BO3)3Si6O18(OH)4)
Hardness 7-7.5 on Mohs scale; color deep black to dark greenish-black; vitreous to resinous luster; trigonal crystal system with prominent vertical striations; perfect to poor cleavage, subconchoidal fracture.
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Physical properties
Hardness 7-7.5 on Mohs scale; color deep black to dark greenish-black; vitreous to resinous luster; trigonal crystal system with prominent vertical striations; perfect to poor cleavage, subconchoidal fracture.
Formation & geological history
Forms in granite pegmatites, hydrothermal veins, and metamorphic rocks under high-temperature and high-pressure geological conditions.
Uses & applications
Used widely in mineral collecting, ornamental carvings, lapidary arts, metaphysical/crystal healing practices, and historically in scientific instruments like pressure gauges due to its piezoelectric qualities.
Geological facts
Black tourmaline exhibits both pyroelectric and piezoelectric properties, meaning it can generate an electrical charge when heated or subjected to mechanical pressure.
Field identification & locations
Identified by its intense black color, high hardness, non-metallic shiny luster, and distinct parallel striations along elongated prismatic crystals. Commonly found in pegmatite-rich regions like Brazil, Madagascar, Pakistan, and the USA (California, Maine).
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Potassium Feldspar (Orthoclase)
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