mineral

Black Tourmaline (Schorl)

NaFe2+3Al6(BO3)3Si6O18(OH)4

Hardness: 7-7.5 on Mohs scale. Color: Deep black to brownish-black. Luster: Vitreous to resinous. Crystal Structure: Trigonal with vertical striations parallel to the C-axis. Cleavage: Indistinct/poor. Specific Gravity: 3.0-3.2.

Hardness: 7-7
Color: Deep black to brownish-black
Luster: Vitreous to resinous

Identified July 27, 2026More mineral →

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Physical properties

Formation & geological history

Forms primarily in granitic pegmatites, hydrothermal veins, and metamorphic rocks such as schists during late-stage crystallization enriched with boron.

Uses & applications

Popular in gemstone jewelry, mineral collections, and metaphysical practices. Historically used in scientific instruments like pressure gauges due to its pyroelectric and piezoelectric properties.

Geological facts

Black tourmaline, also known as Schorl, accounts for nearly 95% of all natural tourmaline found on Earth. It becomes electrically charged when heated (pyroelectric) or subjected to pressure (piezoelectric).

Field identification & locations

Identified in the field by its distinct prismatic, elongated crystal habit with deep vertical striations and triangular cross-section. Commonly found in Brazil, Madagascar, Pakistan, Namibia, and the United States (Maine and California).

Other mineral specimens

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Arenite (SiO2 based)

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Limonite / Goethite (Iron Ore Mineral nodule)

FeO(OH)·nH2O / FeO(OH)

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Schist

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Septarian Pebble

Septarian nodule / Concretion

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Potassium Feldspar (Orthoclase)

Orthoclase (KAlSi3O8)

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Sandstone with Mineral Veining or Crust

Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)

sedimentary