mineral

Tourmaline

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

Hardness: 7 to 7.5 Mohs. Color: Multi-colored (pink, green, yellow, brown). Luster: Vitreous side to resinous. Crystal structure: Trigonal/Hexagonal. Cleavage: Indistinct. Specific gravity: 3.0 to 3.26.

Hardness: 7 to 7
Color: Multi-colored (pink, green, yellow, brown)
Luster: Vitreous side to resinous

Identified March 18, 2026More mineral →

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Physical properties

Formation & geological history

Formed through hydrothermal or magmatic processes, typically in granitic pegmatites or in metamorphic rocks such as marbles or schists. They can be hundreds of millions of years old.

Uses & applications

Commonly used as a gemstone in high-end and artisanal jewelry (necklaces, bracelets, rings). Historically used in pressure gauges due to its piezoelectric properties.

Geological facts

Tourmaline is unique because it displays piezo- and pyroelectric properties, meaning it can generate electric charges when heated or under pressure. It is often called the 'Rainbow Gemstone' due to its vast color spectrum.

Field identification & locations

Identify by its characteristic triangular cross-section in raw crystals and its strong pleochroism. Commonly found in Brazil, Afghanistan, Africa (Nigeria/Madagascar), and the USA (Maine/California).

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Mineral/Rock

Banded Gneiss (River Rock/Pebble)

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Metamorphic Rock

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Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

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