igneous
Granitic Pegmatite with Tourmaline
Granite (Feldspar/Quartz matrix) with Schorl (NaFe2+3Al6Si6O18(BO3)3(OH)3OH)
Hardness 6-7.5; Black (Tourmaline) and white/creamy (Feldspar/Quartz); Vitreous luster; Hexagonal/trigonal black crystals embedded in a crystalline matrix; Poor cleavage; Specific gravity 3.0-3.2
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Physical properties
Hardness 6-7.5; Black (Tourmaline) and white/creamy (Feldspar/Quartz); Vitreous luster; Hexagonal/trigonal black crystals embedded in a crystalline matrix; Poor cleavage; Specific gravity 3.0-3.2
Formation & geological history
Formed during the final stages of a magma body's crystallization, where high water and volatile content allow for the growth of large, distinct minerals. These typically form in dikes or veins.
Uses & applications
Mostly for mineral collecting and educational samples. Schorl is sometimes used in industrial applications for its piezoelectric properties or as a minor gemstone.
Geological facts
Schorl is the most common variety of the tourmaline group, making up about 95% of all tourmaline found in nature. It is heavily iron-rich, which gives it its deep black color.
Field identification & locations
Identify by the contrast of the black, elongated or prismatic crystals against a light-colored felsic matrix. Common in mountain ranges and pegmatite fields globally.
