mineral

Black tourmaline (likely schorl)

Schorl, NaFe3Al6(BO3)3Si6O18(OH)4

AI-generated identification · may be incorrect

Typically black, opaque, and vitreous to resinous, with a prismatic crystal structure and strong longitudinal striations; Mohs hardness 7–7.5, specific gravity about 3.1–3.3, and poor cleavage. The lower dark rounded object may be another polished stone or non-geological object.

Identified August 20, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in boron-rich granitic pegmatites and hydrothermal veins during late-stage igneous crystallization, commonly in Precambrian to younger rocks. The angular specimen’s texture is consistent with a broken or cut tourmaline fragment.

Uses & applications

Used as a collector mineral, ornamental stone, and occasionally in cabochons; black tourmaline is also marketed decoratively and in metaphysical products. It has limited industrial use compared with lithium-rich tourmalines.

Geological facts

Tourmaline is strongly piezoelectric and can become electrically charged when heated or rubbed. Schorl is the most common tourmaline species and is frequently associated with quartz, feldspar, and mica.

Field identification & locations

Identify it by its opaque black color, elongated striated prisms, high hardness, and lack of obvious cleavage; a streak test is usually pale gray to brownish rather than black. Common localities include Brazil, Afghanistan, Madagascar, Namibia, and the United States, especially Maine and California.