mineral
Black tourmaline bead bracelet
Schorl tourmaline, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
AI-generated identification · may be incorrectPolished, nearly black to brown translucent beads with vitreous luster; Mohs hardness 7–7.5, trigonal crystal structure, and indistinct cleavage. The visible brown-gold areas may reflect dravite-rich zoning or surface inclusions.
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Physical properties
Polished, nearly black to brown translucent beads with vitreous luster; Mohs hardness 7–7.5, trigonal crystal structure, and indistinct cleavage. The visible brown-gold areas may reflect dravite-rich zoning or surface inclusions.
Formation & geological history
Tourmaline crystallizes in boron-rich hydrothermal veins, pegmatites, and metamorphic rocks, commonly during Paleozoic–Mesozoic mountain-building events. Major sources include Brazil, Afghanistan, Pakistan, Madagascar, Namibia, and the United States.
Uses & applications
Used as a gemstone, ornamental bead material, and collector mineral; occasionally marketed for purported metaphysical or electrical properties, which lack scientific support. It is not generally used as a construction stone.
Geological facts
Tourmaline is strongly pleochroic and becomes electrically polarized when heated or compressed (pyroelectric and piezoelectric). Schorl is the most common tourmaline species.
Field identification & locations
Identify by its black color, glassy luster, hardness, lack of obvious cleavage, and—on crystal specimens—characteristic striated prismatic form. A bracelet’s beads may be treated or assembled from mixed-quality material, so definitive identification requires testing or laboratory analysis.
