mineral
Black tourmaline pendant
Schorl tourmaline, NaFe3Al6(BO3)3Si6O18(OH)4
AI-generated identification · may be incorrectBlack, opaque, vitreous-to-resinous luster; trigonal crystal structure with strong longitudinal striations and indistinct cleavage. Mohs hardness 7–7.5; specific gravity about 3.1–3.3. The image shows a polished, faceted pendant set in metal.
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Physical properties
Black, opaque, vitreous-to-resinous luster; trigonal crystal structure with strong longitudinal striations and indistinct cleavage. Mohs hardness 7–7.5; specific gravity about 3.1–3.3. The image shows a polished, faceted pendant set in metal.
Formation & geological history
Forms mainly in boron-rich hydrothermal veins and granitic pegmatites, commonly during late-stage granite crystallization. Tourmaline occurs in rocks ranging from Paleozoic to modern geological settings, depending on locality.
Uses & applications
Used as a gemstone, ornamental material, and metaphysical collectible; it is also valued for piezoelectric and pyroelectric properties. This specimen is jewelry rather than a construction stone.
Geological facts
Schorl is the most common tourmaline variety and owes its black color primarily to iron. Heating or pressure can produce electrical charge, a defining tourmaline property.
Field identification & locations
Identify by its black color, glassy luster, elongated striated crystals, high hardness, and lack of obvious cleavage; test cautiously because it is mounted and polished. Common sources include Brazil, Afghanistan, Madagascar, Namibia, and the United States.
