mineral

Likely brown tourmaline (dravite) crystal in matrix

Dravite, a sodium-magnesium tourmaline; ideal formula NaMg₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Dark brown to nearly black, with glassy luster and apparent prismatic crystal faces; tourmaline is trigonal, Mohs hardness 7–7.5, and lacks prominent cleavage. The photo alone does not confirm the identification; the specimen may also be another brown mineral.

Identified October 9, 2026More mineral →

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At a glance

Common name: Likely brown tourmaline (dravite) crystal in matrix
Scientific name: Dravite, a sodium-magnesium tourmaline; ideal formula NaMg₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
Category: mineral
Identified: October 9, 2026
Method: Standard

AI Estimated Value

Approximately $5–$40 for a small, opaque rough specimen; more if confirmed, well-formed, or from a documented locality.

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

Tourmaline commonly crystallizes in pegmatites and boron-rich metamorphic rocks; its age depends on the host deposit and cannot be determined from the image.

Uses & applications

Crystals are collected; transparent, attractive tourmaline is cut for jewelry. Most dark, opaque specimens have modest collector value.

Geological facts

Tourmaline is a complex borosilicate group with substantial chemical variation, which produces many colors.

Field identification & locations

Check for lengthwise striations and a triangular or rounded-triangular cross-section, typical of tourmaline; confirm with hardness and, ideally, mineral testing. Brown tourmaline occurs in deposits worldwide, including Brazil, Sri Lanka, and parts of Africa.