Tourmaline
Image: “Jon Zander (Digon3)" (CC BY-SA 3.0)
Mineral NameTourmaline
Chemical Formula(Na,Ca)(Mg,Fe,Li,Al)3Al6(BO3)3Si6O18(OH,F)4
Mohs Hardness7
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
Cleavageindistinct
Fractureconchoidal to uneven
Specific Gravity3.06
Colorspinkish-brown, black, brown, green, red, blue, yellow, colorless
Transparencytranslucent
Type LocalityBrazil, Afghanistan, Pakistan, USA (Maine, California), Africa
Mineral GroupSilicates (Cyclosilicates)
Usesjewelry, industrial (piezoelectric), collector
Associated Mineralsquartz, feldspar, mica, beryl, topaz
Raritycommon
Description
This specimen features a cluster of elongated, prismatic tourmaline crystals, predominantly pinkish-brown, embedded in a lighter, possibly quartz-rich matrix. The crystals exhibit characteristic vertical striations along their length.
Geological Context
Tourmaline forms in a variety of igneous and metamorphic rocks, most notably in granitic pegmatites and hydrothermal veins, as well as in some metamorphic schists and gneisses.
