mineral

Rough Green Tourmaline (Verdelite)

Elbaite (Complex Borosilicate), Na(Li,Al)3Al6(BO3)3Si6O18(OH)4

Hardness: 7 to 7.5 on Mohs scale. Color: Deep forest green (verdelite). Luster: Vitreous (glassy). Crystal structure: Trigonal/hexagonal with distinct vertical striations. Cleavage: Indistinct. Specific gravity: 3.06.

Hardness: 7 to 7
Color: Deep forest green (verdelite)
Luster: Vitreous (glassy)

Identified March 15, 2026More mineral →

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Physical properties

Formation & geological history

Formed in granitic pegmatites and metamorphic rocks through hydrothermal processes. Most specimens date from the Paleozoic to Mesozoic eras where boron-rich fluids crystallize in cooling magma pockets.

Uses & applications

Used primarily as a gemstone in jewelry (faceted or cabochons). Large, high-clarity crystals are highly prized by mineral collectors. Historically used for its piezoelectric and pyroelectric properties in pressure gauges.

Geological facts

Tourmaline is known as the 'Rainbow Gem' because it occurs in more colors than any other mineral. It is unique for its pyroelectricity—it can develop an electric charge when heated, which causes it to attract dust particles.

Field identification & locations

Identify in the field by the long, needle-like or columnar crystals with vertical grooves (striations) and a rounded triangular cross-section. Common locations include Brazil, Afghanistan, and Maine (USA).

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