mineral
Black tourmaline pendant
Schorl tourmaline, NaFe3Al6(BO3)3Si6O18(OH)4
AI-generated identification · may be incorrectOpaque black, vitreous to resinous luster, commonly prismatic with longitudinal striations and trigonal crystal symmetry; Mohs hardness 7–7.5, no prominent cleavage, specific gravity about 3.1–3.3. The specimen appears polished and shaped as a faceted pendant, likely schorl.
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Physical properties
Opaque black, vitreous to resinous luster, commonly prismatic with longitudinal striations and trigonal crystal symmetry; Mohs hardness 7–7.5, no prominent cleavage, specific gravity about 3.1–3.3. The specimen appears polished and shaped as a faceted pendant, likely schorl.
Formation & geological history
Forms in boron-rich granitic pegmatites and hydrothermal veins through late-stage igneous crystallization, generally in Phanerozoic rocks. Common sources include Brazil, Afghanistan, Madagascar, Pakistan, and the United States.
Uses & applications
Used as an ornamental gemstone, jewelry pendant, mineral specimen, and sometimes in metaphysical products; tourmaline’s piezoelectric and pyroelectric properties also have technical applications.
Geological facts
Tourmaline crystals can develop electrical charges when heated or compressed. Schorl is the most common tourmaline species and is iron-rich, accounting for its deep black color.
Field identification & locations
Identify by its black opaque color, elongated striated prisms, triangular or polygonal cross-section, and strong electrical response when heated or rubbed; distinguish from obsidian by crystal form and striations. The metal cap and chain are non-geological.
