mineral

Black tourmaline (schorl) crystal fragments

Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Typically black to dark brown, vitreous to resinous luster, Mohs hardness 7–7.5, trigonal crystal structure, and no prominent cleavage; prismatic crystals commonly show strong longitudinal striations. The pictured pieces appear to be small, naturally fractured or cut crystal fragments.

Identified September 12, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in granite pegmatites, hydrothermal veins, and metamorphic rocks during late-stage igneous crystallization; specimens range from Precambrian to modern geological settings. Common sources include Brazil, Afghanistan, Pakistan, Madagascar, Namibia, and the United States.

Uses & applications

Used as mineral specimens, in jewelry, and occasionally as a piezoelectric or technical material; gem-quality transparent tourmaline varieties are more valuable than opaque schorl.

Geological facts

Tourmaline is strongly piezoelectric and can become electrically charged when heated or compressed. Black schorl is the most abundant tourmaline variety.

Field identification & locations

Identify it by the black prismatic form, lengthwise grooves, glassy luster, and hardness greater than ordinary steel; confirm with a streak, hardness, and specific-gravity test. The image alone cannot exclude similarly shaped hornblende or manufactured metal fragments.