mineral

Dark polished stone, possibly black tourmaline or dark quartzite

Uncertain from the image; possible schorl (NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄) or quartz-rich rock

AI-generated identification · may be incorrect

Two small, dark gray-black, polished pieces with a subdued luster; visible features are insufficient to determine hardness, crystal structure, or cleavage. The upper piece shows faint pale veining or scratches.

Identified September 26, 2026More mineral →

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At a glance

Common name: Dark polished stone, possibly black tourmaline or dark quartzite
Scientific name: Uncertain from the image; possible schorl (NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄) or quartz-rich rock
Category: mineral
Identified: September 26, 2026
Method: Standard

AI Estimated Value

Approximately $1–$10 for small, common polished pieces; higher value would require confirmed identity and notable 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

If tourmaline, it typically crystallized in granitic pegmatites; if quartzite, it formed by metamorphism of quartz sandstone. Age and origin cannot be established visually.

Uses & applications

Small polished specimens are commonly kept as collectibles or used in jewelry and crafts; identification is needed to establish any specific industrial use.

Geological facts

Dark polished stones can look alike in photographs, and a scratch, streak, or mineral test is often needed for reliable identification.

Field identification & locations

Check hardness, streak, density, and any crystal faces; tourmaline is typically harder than a knife and has lengthwise striations, while quartzite is granular and very hard. Both occur in many regions worldwide.