Black Tourmaline

Physical Properties

Hardness: 7-7.5 (Mohs scale), Color: Jet black to brownish-black, Luster: Vitreous to sub-metallic, Crystal Structure: Trigonal, Cleavage: Indistinct, Specific Gravity: 3.0-3.3

Formation & Geological History

Formed in igneous pegmatites, hydrothermal veins, and metamorphic rocks such as schists and marbles. It is a complex borosilicate mineral that forms during the late stages of magma crystallization.

Uses & Applications

Used in electronics for its pyroelectric and piezoelectric properties, in water filtration systems, and heavily used in jewelry and crystal collecting.

Geological Facts

Black tourmaline is known for its pyroelectricity, meaning it becomes electrically charged when heated; it was historically used by Dutch traders to pull ash out of clay pipes and was called 'aschentrekker' (ash puller).

Field Identification & Locations

Identify by its deep black color, lack of cleavage, and vertical striations on crystal faces. Common in granitic pegmatites. Collectors look for high luster and lack of cracks.

Identified on: 4/28/2026

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