mineral

Black tourmaline in quartz (schorl-bearing specimen)

Schorl tourmaline, NaFe2+3Al6Si6O18(BO3)3(OH)4, with quartz, SiO2

AI-generated identification · may be incorrect

Schorl is black, opaque, and commonly striated with vitreous-to-subvitreous luster; hardness 7–7.5, trigonal crystal structure, and poor cleavage. The pale translucent matrix is likely quartz, hardness 7, with characteristic conchoidal fracture.

Identified September 16, 2026More mineral →

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Physical properties

Formation & geological history

Typically forms in granitic pegmatites and hydrothermal veins during late-stage cooling of silica-rich magma, generally in Precambrian to Phanerozoic terrains. The specimen appears naturally fractured rather than polished.

Uses & applications

Collected as a mineral specimen; attractive pieces are used in lapidary work and occasionally jewelry. Tourmaline is also studied for its piezoelectric and pyroelectric properties.

Geological facts

Schorl is the most common tourmaline species and is strongly pleochroic in transparent crystals. Heating or pressure can produce electrical charges at opposite crystal ends.

Field identification & locations

Identify it by black, lengthwise-striated prismatic crystals, triangular cross-sections, and quartz association; distinguish it from hornblende by tourmaline’s strong striations and lack of prominent cleavage. Common sources include Brazil, Afghanistan, Pakistan, Madagascar, and the United States.