igneous
Black Tourmaline in Quartz and Feldspar Matrix
Schorl (NaFe3Al6(BO3)3Si6O18(OH)4) with Quartz and Feldspar
Hardness: 7 (Tourmaline) / 7 (Quartz) / 6 (Feldspar). Color: Black crystals in white/translucent matrix. Lustre: Vitreous to sub-metallic. Crystal Structure: Trigonal (Tourmaline). Cleavage: Imperfect to none (Schorl). Specific Gravity: 3.0-3.25.
- Hardness
- 7 (Tourmaline) / 7 (Quartz) / 6 (Feldspar)
- Color
- Black crystals in white/translucent matrix
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Tourmaline) / 7 (Quartz) / 6 (Feldspar). Color: Black crystals in white/translucent matrix. Lustre: Vitreous to sub-metallic. Crystal Structure: Trigonal (Tourmaline). Cleavage: Imperfect to none (Schorl). Specific Gravity: 3.0-3.25.
Formation & geological history
Formed in granitic pegmatites through the slow cooling of magma rich in boron and silica. This typically occurs in late-stage igneous crystallization in continental crust environments.
Uses & applications
Schorl is used in industrial applications for its piezoelectric properties and as a popular semi-precious stone for collectors and metaphysical practices. Quartz and feldspar are used in glass and ceramic industries.
Geological facts
Schorl is the most common member of the tourmaline group, accounting for 95% of all tourmaline in nature. It is naturally pyroelectric, meaning it develops an electrical charge when heated.
Field identification & locations
Identify by the characteristic triangular/hemispherical cross-section of the black crystals and vertical striations along the prism faces. Found frequently in pegmatitic outcrops globally.
