mineral

Polished black tourmaline (likely schorl)

Schorl, a sodium-rich tourmaline-group mineral; approximate formula NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

A smooth, highly polished dark green-black sphere with a vitreous-to-glassy luster. Tourmaline is typically Mohs 7–7.5, trigonal, and has poor basal cleavage; the photo cannot confirm the material or internal structure, so identification is tentative.

Identified October 8, 2026More mineral →

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Physical properties

Formation & geological history

Tourmaline commonly crystallizes in granitic pegmatites and hydrothermal veins; its age depends on the deposit and cannot be determined from a polished specimen. Sri Lanka is known for gem-bearing pegmatites and alluvial gem deposits, making tourmaline regionally plausible.

Uses & applications

Used as a decorative sphere, collectible, and sometimes in jewelry; tourmaline is also valued as a gemstone.

Geological facts

Schorl is the most common tourmaline species and is usually black. Polishing hides the crystal form and makes visual identification less certain.

Field identification & locations

Look for hardness, a streak that is usually pale, and—on rough crystals—distinct lengthwise striations; testing a polished piece risks damage. Confirm with gemological testing, since other black stones can look similar.