igneous
Pegmatite with Black Tourmaline
Granitic Pegmatite with Schorl (NaFe2+3Al6(Si6O18)(BO3)3(OH)3OH)
Hardness: 7-7.5 (Tourmaline), 6-6.5 (Feldspar); Color: Black crystals in white/pink matrix; Luster: Vitreous to sub-metallic; Crystal Structure: Trigonal (Tourmaline crystals), Monoclinic/Triclinic (Matrix); Cleavage: Indistinct; Specific Gravity: Approx 2.6-3.2.
- Hardness
- 7-7
- Color
- Black crystals in white/pink matrix
- Luster
- Vitreous to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 7-7.5 (Tourmaline), 6-6.5 (Feldspar); Color: Black crystals in white/pink matrix; Luster: Vitreous to sub-metallic; Crystal Structure: Trigonal (Tourmaline crystals), Monoclinic/Triclinic (Matrix); Cleavage: Indistinct; Specific Gravity: Approx 2.6-3.2.
Formation & geological history
Formed during the final stages of a magma chamber's crystallization, where water-rich fluids allow for the growth of large crystals. Found in granitic intrusions and metamorphic belts worldwide.
Uses & applications
Tourmaline is used as a gemstone, for its piezoelectric properties in electronics, and as a popular mineral specimen for collectors. Pegmatite is a source of rare earth elements, lithium, and industrial quartz.
Geological facts
Black tourmaline, or Schorl, is the most common variety of tourmaline and accounts for 95% of all tourmaline found in nature. It is often believed by collectors to provide 'grounding' or protection from negative energy.
Field identification & locations
Identified by the needle-like or columnar black crystals embedded in a light-colored matrix of quartz or feldspar. Often found in mountainous regions with exposed granitic batholiths. Collectors look for well-defined hexagonal terminations in the black crystals.
