mineral

Likely raw tourmaline crystal (black schorl)

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

AI-generated identification · may be incorrect

Identified September 10, 2026More mineral →

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At a glance

Common name: Likely raw tourmaline crystal (black schorl)
Scientific name: Schorl, black tourmaline — complex boron silicate, commonly approximated as NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
Category: mineral
Identified: September 10, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a common rough piece of this size; $30–$150+ for unusually well-formed, locality-labeled crystals.

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

Opaque black, strongly vitreous to submetallic luster with longitudinal striations and a prismatic/ribbed habit; Mohs hardness 7–7.5, trigonal crystal structure, no prominent cleavage, specific gravity about 3.0–3.3. The specimen appears naturally rough or partly weathered, though the image is not sufficient for certainty.

Formation & geological history

Forms in granite pegmatites and hydrothermal veins during late-stage igneous crystallization, commonly in Paleozoic to younger continental crust. It may also occur as resistant detrital grains in sediments.

Uses & applications

Used as a collectible mineral and, when transparent, as a gemstone; black schorl is also sold for ornamental and metaphysical purposes. It has limited industrial use compared with tourmaline’s piezoelectric applications.

Geological facts

Tourmaline crystals can become electrically polarized when heated or compressed (pyroelectric and piezoelectric effects). Longitudinal striations are one of its most useful visual clues.

Field identification & locations

Common localities include Brazil, Afghanistan, Pakistan, Madagascar, Namibia, and the United States, especially Maine and California. Confirm with a hardness test, crystal striations, density, and possible electrical response; avoid damaging valuable specimens.