mineral
Black Tourmaline (Schorl)
Schorl (NaFe3Al6(BO3)3Si6O18(OH)4)
Hardness: 7-7.5. Color: Jet black. Luster: Vitreous to sub-metallic. Crystal system: Trigonal. Cleavage: Indistinct. Specific gravity: 3.0-3.2. Form: Long prismatic with vertical striations.
- Hardness
- 7-7
- Color
- Jet black
- Luster
- Vitreous to sub-metallic
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Physical properties
Hardness: 7-7.5. Color: Jet black. Luster: Vitreous to sub-metallic. Crystal system: Trigonal. Cleavage: Indistinct. Specific gravity: 3.0-3.2. Form: Long prismatic with vertical striations.
Formation & geological history
Formed in granitic pegmatites, hydrothermal veins, and metamorphic rocks like schist. Created during late-stage crystallization of magma enriched with boron.
Uses & applications
Industrial use in pressure gauges (piezoelectric properties), ornamental carvings, and widely used in jewelry and metaphysical collections.
Geological facts
Black tourmaline is both pyroelectric (generates electricity when heated) and piezoelectric (generates electricity under pressure). Because of these properties, it can attract dust and small particles.
Field identification & locations
Identified by its jet-black color, triangular cross-section (often rounded), and deep vertical striations on crystal faces. Common in Brazil, Namibia, and the USA.
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Arenite (SiO2 based)
sedimentary
Sandstone with Mineral Veining or Crust
Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)
sedimentary
Schist
Schist
Metamorphic
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
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