mineral

Black tourmaline (schorl), probable

Schorl tourmaline, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Typically black, opaque, vitreous to submetallic, with prismatic crystals and strong lengthwise striations; Mohs hardness 7–7.5, specific gravity about 3.0–3.3, and poor-to-indistinct cleavage. The photograph shows a dark, striated fragment, though identification is not definitive without testing.

Identified September 16, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in granitic pegmatites and hydrothermal veins during late-stage magma crystallization, commonly in Precambrian to younger igneous terrains. It may also occur as resistant grains in sedimentary deposits.

Uses & applications

Used as a collector mineral, gemstone, and occasionally in metaphysical products; gem-quality transparent tourmaline is cut for jewelry, while opaque schorl is mainly ornamental.

Geological facts

Tourmaline is strongly piezoelectric and becomes electrically charged when heated or pressured. Black schorl is the most abundant tourmaline variety.

Field identification & locations

Look for black color, longitudinal striations, glassy luster, and lack of acid reaction; hardness can scratch glass, but this is not diagnostic. Common localities include Brazil, Afghanistan, Madagascar, Namibia, and the United States.