mineral

Black tourmaline (schorl), likely polished or tumbled

Schorl tourmaline — complex borosilicate, commonly approximated as NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Opaque black, vitreous to resinous luster, uneven fracture and commonly strong prismatic striations; Mohs hardness 7–7.5, specific gravity about 3.0–3.3. The image shows a dense dark specimen with a rough-polished surface; crystal faces are not clearly visible.

Identified September 4, 2026More mineral →

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At a glance

Common name: Black tourmaline (schorl), likely polished or tumbled
Scientific name: Schorl tourmaline — complex borosilicate, commonly approximated as NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
Category: mineral
Identified: September 4, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a common polished or rough specimen; $30–$150+ for attractive large crystals or quality carvings.

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 granitic pegmatites and hydrothermal veins as late-stage crystals, typically in Precambrian to Phanerozoic rocks. Associated minerals include quartz, feldspar, mica, and lepidolite.

Uses & applications

Used as a collector mineral, ornamental stone, beads, carvings, and occasionally jewelry; gem-quality transparent tourmaline is more valuable than opaque schorl.

Geological facts

Tourmaline is piezoelectric and can become electrically charged when heated or pressed. Schorl is the most common tourmaline species and is generally iron-rich.

Field identification & locations

Identify it by black color, high hardness, elongated striated crystals, and inability to scratch it with a steel knife easily; a streak test is usually pale or colorless. Common localities include Brazil, Afghanistan, Pakistan, the United States, Madagascar, and Namibia.