igneous
Schorl (Black Tourmaline) in Quartz or Feldspar Matrix
NaFe3Al6(BO3)3Si6O18(OH)4 (Schorl) in Granitic Pegmatite
Hardness: 7-7.5 (Tourmaline) / 6-7 (Matrix). Color: Jet black needle-like crystals in a tan/white matrix. Luster: Vitreous to resinous. Crystal structure: Trigonal (hexagonal prisms). Cleavage: None/Indistinct.
- Hardness
- 7-7
- Color
- Jet black needle-like crystals in a tan/white matrix
- Luster
- Vitreous to resinous
Identified More igneous →
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Physical properties
Hardness: 7-7.5 (Tourmaline) / 6-7 (Matrix). Color: Jet black needle-like crystals in a tan/white matrix. Luster: Vitreous to resinous. Crystal structure: Trigonal (hexagonal prisms). Cleavage: None/Indistinct.
Formation & geological history
Formed in granitic pegmatites during the final stages of magma crystallization. Rich in boron; found in intrusive igneous environments typically ranging from Proterozoic to Cenozoic eras.
Uses & applications
Commonly used for mineral collecting and as a 'healing crystal' in metaphysical circles. Historically used as a source of boron; high-quality specimens may be used as cabochons in jewelry.
Geological facts
Tourmaline is pyroelectric, meaning it generates an electrical charge when heated. It is also piezoelectric, generating a charge under mechanical stress. Schorl accounts for approximately 95% of all tourmaline found in nature.
Field identification & locations
Identify by the elongated, columnar, or needle-like black crystals embedded in light-colored rock. Look for vertical striations along the crystal faces. Common in Brazil, Namibia, and the USA (California/Maine).
