mineral
Black Tourmaline (Schorl)
NaFe3+3Al6(BO3)3Si6O18(OH)4
Hardness 7.0-7.5 on Mohs scale, deep black color, vitreous to resinous luster, trigonal/prismatic crystal structure with distinct vertical striations, uneven to conchoidal fracture.
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Physical properties
Hardness 7.0-7.5 on Mohs scale, deep black color, vitreous to resinous luster, trigonal/prismatic crystal structure with distinct vertical striations, uneven to conchoidal fracture.
Formation & geological history
Formed in igneous pegmatites, metamorphic rocks, and hydrothermally altered granites through boron-bearing fluid activity during late-stage crystallization.
Uses & applications
Popular for lapidary work, specimen collections, metaphysical usage as a protective stone, and historical scientific experiments involving its pyroelectric and piezoelectric properties.
Geological facts
Black tourmaline, also known as Schorl, accounts for nearly 95% of all natural tourmaline on Earth. When heated or rubbed, it develops an electric charge that attracts light particles like dust.
Field identification & locations
Identify in the field by its dark black color, high hardness, parallel striations along elongated prismatic crystals, and triangular cross-section. Widely found in Brazil, Madagascar, Pakistan, and the USA.
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