mineral

Banded tourmaline (likely schorl)

Black tourmaline, primarily schorl; complex borosilicate, commonly NaFe3Al6(BO3)3Si6O18(OH)4

AI-generated identification · may be incorrect

Black, opaque, strongly vitreous to submetallic luster with prominent longitudinal striations and prismatic cleavage/fracture; Mohs hardness 7–7.5, specific gravity about 3.0–3.3. The visible parallel bands may reflect crystal growth zoning or matrix layering.

Identified September 16, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in granite pegmatites and hydrothermal veins during late-stage igneous crystallization, generally in Phanerozoic continental crust. Exact age and locality cannot be determined from the photograph.

Uses & applications

Used as a collector specimen, ornamental stone, and occasionally in jewelry; tourmaline’s piezoelectric and pyroelectric properties have specialized technical applications.

Geological facts

Tourmaline crystals can become electrically charged when heated or compressed. Schorl is the most common tourmaline species and is iron-rich, producing its black color.

Field identification & locations

Identify by the black prismatic habit, lengthwise striations, hardness, and inability to scratch it with a steel knife easily; quartz or mica may be associated. Common localities include Brazil, Afghanistan, Pakistan, Madagascar, Namibia, and the United States.