mineral

Black tourmaline (schorl), possibly with mica/quartz

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

AI-generated identification · may be incorrect

Typically black, vitreous to submetallic, with irregular fracture and commonly prismatic crystal structure; Mohs hardness 7–7.5 and specific gravity about 3.0–3.3. The specimen appears coarse and massive, with reflective cleavage-like surfaces and possible attached matrix minerals.

Identified September 4, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in boron-rich granitic pegmatites and hydrothermal veins during late-stage igneous crystallization, commonly in Precambrian to younger continental crust. Exact age and locality cannot be determined from the photograph.

Uses & applications

Used as a collector mineral and occasionally as a gemstone when transparent and well formed; low-grade material has limited industrial value. It is not normally used as construction stone.

Geological facts

Schorl is the most common tourmaline species and is often strongly black because of iron. Tourmaline is piezoelectric and pyroelectric, developing electrical charge when heated or stressed.

Field identification & locations

Identify it by its black color, glassy luster, hardness, and lengthwise striations on prismatic crystals; quartz and mica may occur alongside it. Common localities include Brazil, Afghanistan, Pakistan, Madagascar, Namibia, and U.S. pegmatites such as Maine and California.