mineral

Polished black-and-white tourmaline

Schorl tourmaline, complex borosilicate; commonly black schorl with quartz or feldspar inclusions

AI-generated identification · may be incorrect

Typically Mohs 7–7.5, black to dark gray with pale gray/white internal streaks, vitreous luster, and trigonal crystal structure; polished specimens have no visible cleavage and a specific gravity around 3.0–3.3.

Identified September 3, 2026More mineral →

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At a glance

Common name: Polished black-and-white tourmaline
Scientific name: Schorl tourmaline, complex borosilicate; commonly black schorl with quartz or feldspar inclusions
Category: mineral
Identified: September 3, 2026
Method: Standard

AI Estimated Value

About $5–$25 for a small polished common cabochon; $30–$150+ for attractive natural banding, provenance, or fine specimen quality.

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 in granitic pegmatites and metamorphic veins as hydrothermal boron-rich fluids crystallize, generally during Precambrian to Phanerozoic tectonic events. Common sources include Brazil, Afghanistan, Madagascar, Namibia, and the United States.

Uses & applications

Used as a gemstone, cabochon, ornamental stone, and mineral specimen; tourmaline is also valued for its piezoelectric and pyroelectric properties. Small polished pieces typically have modest decorative value.

Geological facts

The pale bands may be quartz, feldspar, or another tourmaline zone, so exact identification from the photograph is uncertain. Tourmaline crystals can develop electrical charges when heated or compressed.

Field identification & locations

Identify by its very dark color, strong polish, hardness, and often striated or banded appearance; a streak test, hardness test, and magnification can distinguish it from obsidian or dyed glass. Look for prismatic, longitudinally striated crystals in pegmatites.