mineral

Black tourmaline

Schorl, NaFe3Al6(BO3)3Si6O18(OH)4

AI-generated identification · may be incorrect

Hardness 7–7.5 Mohs; opaque black color, vitreous to resinous luster, and elongated prismatic crystals with strong vertical striations. It has poor cleavage and commonly forms triangular or rounded three-sided cross-sections; specific gravity is about 3.1–3.3.

Identified September 5, 2026More mineral →

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Physical properties

Formation & geological history

Forms in boron-rich hydrothermal veins, granitic pegmatites, and metamorphic rocks during late-stage crystallization, commonly from Paleozoic to younger geological settings. The pictured crystal appears natural, though its exact locality cannot be determined from the image.

Uses & applications

Used as a collector mineral, lapidary material, and occasionally in jewelry; fine crystals can be valuable, while most pieces are inexpensive.

Geological facts

Schorl is the most common tourmaline species and is strongly piezoelectric and pyroelectric, producing electrical charge when heated or pressured.

Field identification & locations

Identify it by its jet-black, striated prismatic form and resistance to scratching by a steel knife. Common localities include Brazil, Afghanistan, Pakistan, Madagascar, Namibia, and the United States, especially Maine and California.