mineral

Black tourmaline in matrix (probable schorl)

Schorl tourmaline, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄, with a yellow-brown iron-oxide-rich vein or alteration mineral

AI-generated identification · may be incorrect

Identified September 3, 2026More mineral →

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At a glance

Common name: Black tourmaline in matrix (probable schorl)
Scientific name: Schorl tourmaline, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄, with a yellow-brown iron-oxide-rich vein or alteration mineral
Category: mineral
Identified: September 3, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a small common specimen; $30–$150+ if the tourmaline is well crystallized and the contrasting matrix is attractive.

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

The rounded black specimen has a vitreous-to-submetallic luster and likely Mohs hardness 7–7.5; tourmaline is trigonal and commonly shows prismatic striations, though this appears tumbled or naturally worn. The contrasting orange-brown material may be limonite/goethite or weathered feldspar, rather than a second confirmed mineral.

Formation & geological history

Tourmaline commonly crystallizes in boron-rich granitic pegmatites and hydrothermal veins, typically during Precambrian to Phanerozoic igneous activity. The brown patch likely formed through later oxidation or fracture infilling.

Uses & applications

Black tourmaline is popular in mineral collections, carvings, cabochons, and inexpensive jewelry; it has limited industrial use. Small common specimens generally have modest value.

Geological facts

Schorl is the most abundant tourmaline species and is strongly pleochroic; tourmaline crystals can become electrically polarized when heated or compressed (the pyroelectric and piezoelectric effects).

Field identification & locations

Look for black prismatic crystals, lengthwise striations, glassy luster, and hardness sufficient to scratch glass; a streak test and locality information would improve identification. Common sources include Brazil, Afghanistan, Madagascar, Namibia, and the United States.