mineral

Black tourmaline (likely schorl), polished

Schorl tourmaline — NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Very dark black, vitreous luster, polished/prismatic appearance, and commonly excellent transparency to translucency at thin edges. Hardness 7–7.5 Mohs; trigonal crystal system; indistinct cleavage; specific gravity about 3.0–3.3.

Identified August 20, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in granitic pegmatites and hydrothermal veins as boron-rich magma cools; most specimens are Precambrian to Mesozoic or younger, depending on locality. The pictured piece appears cut and polished rather than naturally crystal-faced.

Uses & applications

Used as a gemstone, ornamental stone, and collector specimen; also marketed for metaphysical purposes. Common black tourmaline has modest jewelry value unless exceptionally clean, large, or well-formed.

Geological facts

Schorl is the most abundant tourmaline species and often shows strong pleochroism and piezoelectricity. Its elongated crystals commonly have vertically striated prism faces and triangular cross-sections.

Field identification & locations

Common sources include Brazil, Afghanistan, Pakistan, Namibia, Madagascar, and the United States (especially Maine and California). Confirm with hardness, a striated prismatic form, and black streak; glassy black look-alikes include obsidian and manufactured glass.