mineral

Polished black stone, likely hematite or black tourmaline

Hematite (Fe₂O₃) or schorl tourmaline (NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄)

AI-generated identification · may be incorrect

Small, rounded, highly polished dark specimen with a submetallic to vitreous luster; hematite has Mohs hardness 5–6.5, while black tourmaline is 7–7.5. The photograph is insufficient to distinguish them reliably; no crystal faces or diagnostic streak are visible.

Identified September 12, 2026More mineral →

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At a glance

Common name: Polished black stone, likely hematite or black tourmaline
Scientific name: Hematite (Fe₂O₃) or schorl tourmaline (NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄)
Category: mineral
Identified: September 12, 2026
Method: Standard

AI Estimated Value

Approximately $2–$15 as a small polished common specimen; substantially more only if confirmed as high-quality gem tourmaline.

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

Hematite forms in hydrothermal veins, sedimentary iron formations, and weathering zones; tourmaline crystallizes in granitic pegmatites and metamorphic rocks. Both range from Precambrian to modern geological settings.

Uses & applications

Polished hematite is used in carvings, jewelry, and pigment; tourmaline is used as a gemstone and collector mineral. Industrial use is generally minor for specimens of this size.

Geological facts

Hematite produces a distinctive red-brown streak, whereas black tourmaline typically gives a white streak and may show longitudinal striations or prismatic crystal form.

Field identification & locations

Test an inconspicuous area on unglazed porcelain: red-brown streak suggests hematite; white streak suggests tourmaline or another dark stone. Common sources include Brazil, the United States, Australia, and Africa.