mineral

Tumbled black tourmaline (likely schorl)

Schorl, sodium–iron tourmaline: NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Very dark brown-black, vitreous to resinous luster, commonly opaque, with an elongated trigonal crystal structure and no obvious cleavage; Mohs hardness 7–7.5, specific gravity about 3.1–3.3. The smooth shape indicates tumbling or polishing, and the brown-golden crust may be matrix or weathering.

Identified September 5, 2026More mineral →

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At a glance

Common name: Tumbled black tourmaline (likely schorl)
Scientific name: Schorl, sodium–iron tourmaline: NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
Category: mineral
Identified: September 5, 2026
Method: Standard

AI Estimated Value

Approximately $5–$25 for a common tumbled piece; $30–$100+ if unusually large, well-polished, or associated with attractive mineral matrix.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Forms mainly in granite pegmatites and hydrothermal veins during late-stage igneous crystallization, generally in Phanerozoic or older continental crust. Common sources include Brazil, Namibia, Afghanistan, Pakistan, Madagascar, and the United States.

Uses & applications

Used as a collector mineral, ornamental stone, and occasionally in jewelry; tourmaline’s electrical and piezoelectric properties also support technical applications. This specimen appears primarily decorative.

Geological facts

Tourmaline is strongly pleochroic and can become electrically charged when heated or rubbed (the origin of its name, linked to ‘mixed colors’). Schorl is the most common tourmaline species.

Field identification & locations

Identify by its black elongated form, high hardness, lack of cleavage, and often striated prism faces; a glass scratch test and a strong neodymium-magnet response may help, though polishing obscures features. Confirmatory identification requires testing or microscopy.