igneous
Schorl (Black Tourmaline) in Quartz/Feldspar Matrix
NaFe3Al6(BO3)3Si6O18(OH)4 (Schorl)
Hardness: 7 (Tourmaline) / 6 (Feldspar). Color: Black elongated crystals in a creamy white to tan matrix. Luster: Vitreous to sub-metallic. Crystal structure: Trigonal (hexagonal prisms with vertical striations).
- Hardness
- 7 (Tourmaline) / 6 (Feldspar)
- Color
- Black elongated crystals in a creamy white to tan matrix
- Luster
- Vitreous to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 7 (Tourmaline) / 6 (Feldspar). Color: Black elongated crystals in a creamy white to tan matrix. Luster: Vitreous to sub-metallic. Crystal structure: Trigonal (hexagonal prisms with vertical striations).
Formation & geological history
Formed in granitic pegmatites during the late stages of magmatic crystallization where boron-rich fluids are concentrated. Usually found in ancient continental crustal rocks.
Uses & applications
Used primarily as a gemstone for collectors and in metaphysical jewelry. Industrially, tourmalines were historically used for their pyroelectric and piezoelectric properties.
Geological facts
Black tourmaline is known as Schorl and is the most common variety of the tourmaline group, comprising about 95% of all tourmaline in nature. It contains high concentrations of iron.
Field identification & locations
Identify in the field by the long, needle-like black crystals with vertical striations (grooves) along the faces. Commonly found in California, Brazil, and Namibia. Tips: check for a triangular-shaped cross-section of the black crystals.
