gemstone

Green tourmaline crystal (probable)

Elbaite tourmaline, complex borosilicate; approximate formula Na(Li,Al)₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Small, rough, prismatic crystal with a dark green-to-brown appearance and vitreous luster; tourmaline is typically Mohs 7–7.5, trigonal, and lacks prominent cleavage. The image is insufficient for certain identification, and it could also be another green mineral or glassy fragment.

Identified August 13, 2026More gemstone →

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Physical properties

Formation & geological history

Usually forms in lithium-rich granite pegmatites through late-stage hydrothermal crystallization, commonly during the Paleozoic–Mesozoic and younger geological events. Green tourmaline occurs worldwide, notably in Brazil, Afghanistan, Pakistan, Madagascar, and the United States.

Uses & applications

Gem-quality material is faceted or cabochon-cut; ordinary crystals are collector specimens. It is also valued for its piezoelectric and pyroelectric properties, though industrial use is limited.

Geological facts

Tourmaline can develop electrical charges when heated or rubbed, attracting dust or small particles. Color zoning and striated prismatic faces are characteristic of many crystals.

Field identification & locations

Look for a strongly striated, three- or six-sided prism, glassy luster, and possible color zoning; hardness testing, magnification, and refractive-index measurements are recommended. Common localities include pegmatites in Minas Gerais, Brazil, and California and Maine, USA.