mineral
Tourmaline (Mixed colors)
Boron silicate mineral (Na,Ca)(Li,Mg,Al,Fe,Mn,Ti,V,Cr)3Al6(BO3)3Si6O18(OH,F)4
AI-generated identification · may be incorrectMohs hardness: 7 to 7.5; Color: Virtually every color (pink, green, blue, black, yellow); Luster: Vitreous; Crystal structure: Trigonal; Cleavage: Indistinct; Specific Gravity: 3.06
- Hardness
- 7 to 7
- Color
- Virtually every color (pink, green, blue, black, yellow)
- Luster
- Vitreous
Identified More mineral →
Explore Tourmaline (Mixed colors) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Mohs hardness: 7 to 7.5; Color: Virtually every color (pink, green, blue, black, yellow); Luster: Vitreous; Crystal structure: Trigonal; Cleavage: Indistinct; Specific Gravity: 3.06
Formation & geological history
Commonly forms in granitic pegmatites and metamorphic rocks like schist and marble. It crystallizes from hydrothermal fluids during the late stages of magmatic cooling.
Uses & applications
Widely used as a gemstone in jewelry, especially when transparent. It is also used in pressure gauges due to its piezoelectric properties and in scientific instruments.
Geological facts
Tourmaline is both pyroelectric and piezoelectric, meaning it can generate an electrical charge when heated or compressed. It was once used by Dutch traders to pull ash out of their tobacco pipes.
Field identification & locations
Identify in the field by its characteristic rounded triangular cross-section and vertical striations along the prism faces. Found globally, with major deposits in Brazil, Madagascar, and Afghanistan.
