mineral

Black tourmaline (schorl) crystal fragment

Schorl, a sodium–iron tourmaline; approximate formula NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Black, opaque, vitreous to submetallic luster, with lengthwise striations and a trigonal crystal structure; Mohs hardness 7–7.5 and no distinct cleavage. The visible piece is a small prismatic crystal fragment.

Identified October 10, 2026More mineral →

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Physical properties

Formation & geological history

Tourmaline commonly crystallizes in granitic pegmatites and some metamorphic rocks as magma cools or fluids alter surrounding rock. Deposits range from Precambrian to geologically recent; the specimen’s age cannot be determined from the image.

Uses & applications

Used as a collectible mineral and, when clear and attractive, in jewelry; tourmaline is also studied for its electrical properties.

Geological facts

Schorl is the most common tourmaline species and is often strongly striated along its crystal length.

Field identification & locations

Look for a black, ridged, elongated prism with a roughly triangular cross-section; common sources include Brazil, Afghanistan, Pakistan, and the United States. The image alone cannot confirm species or locality.