mineral

Polished black tourmaline (schorl), likely a carved or polished specimen

Schorl, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Black to very dark brown with a vitreous-to-submetallic polish and elongated striations; hardness 7–7.5 Mohs, trigonal crystal structure, poor cleavage, and specific gravity about 3.0–3.3. The photo does not show enough detail to confirm the identification; other dark minerals are possible.

Identified September 24, 2026More mineral →

Explore Polished black tourmaline (schorl), likely a carved or polished specimen in the encyclopedia →

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Physical properties

Formation & geological history

Tourmaline forms in boron-rich granitic pegmatites and metamorphic rocks, crystallizing as magma cools or during fluid-driven alteration. Its age depends on the deposit, commonly spanning Precambrian to much younger geological settings.

Uses & applications

Used as a collector’s and ornamental stone, in jewelry, and occasionally as a source of tourmaline for mineral specimens.

Geological facts

Schorl is the most common tourmaline species; tourmalines can develop electrical charge when heated or compressed (pyroelectric and piezoelectric effects).

Field identification & locations

Look for a black color and lengthwise grooves on prismatic crystals; hardness and striations help distinguish it from softer dark minerals. Tourmaline occurs worldwide, notably in Brazil, Afghanistan, Pakistan, and the United States.