mineral

Tumbled schorl tourmaline

Black tourmaline (schorl), complex borosilicate: NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Hardness 7–7.5 Mohs; black to dark brown, commonly vitreous to submetallic luster, with elongated prismatic crystal structure and strong vertical striations. The rounded form appears polished or naturally water-worn; cleavage is poor and fracture uneven.

Identified September 9, 2026More mineral →

Explore Tumbled schorl tourmaline in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Forms in boron-rich granitic pegmatites and hydrothermal veins, commonly during late-stage crystallization of Paleozoic–Mesozoic granitic systems, though specimens occur in rocks of many ages. The ridged texture reflects tourmaline’s lengthwise crystal growth.

Uses & applications

Used as a collectible and ornamental stone, in cabochons and carvings, and occasionally in electrical or pressure-sensing applications because tourmaline is piezoelectric and pyroelectric.

Geological facts

Schorl is the most common tourmaline species and its black color results mainly from iron. It can become electrically charged when heated or rubbed.

Field identification & locations

Identify it by its opaque black color, longitudinal grooves, glassy luster, and resistance to scratching by steel; confirm with a hardness and streak test when appropriate. Common sources include Brazil, Afghanistan, Pakistan, Madagascar, Namibia, and the United States.