Image: <a href="//commons.wikimedia.org/wiki/User:AdamStejskal" title="User:AdamStejskal">AdamStejskal</a> (CC BY 4.0)
trigonalcommonSilicates
Tourmaline
(Na,Ca)(Li,Mg,Fe,Mn,Al)3Al6(BO3)3Si6O18(OH,F)4
The image displays several well-formed, black, prismatic tourmaline crystals, likely a mix of schorl and dravite, with distinct, fully terminated tops, on a light-colored matrix.
Tourmaline Physical Properties
Mohs Hardness
7Crystal System
trigonalLuster
vitreousStreak Color
whiteCleavage
indistinct/poor basalFracture
uneven to conchoidalSpecific Gravity
3.06Colors
black, brown, green, pink, red, blue, yellow, colorlessTransparency
transparent to opaqueType Locality
Pikarec, Czech RepublicMineral Group
SilicatesUses
jewelry, collector, industrialAssociated Minerals
quartz, feldspar, mica, beryl, topazRarity
commonGeological Context
Tourmaline is a complex borosilicate mineral that forms in igneous and metamorphic rocks, most commonly in granitic pegmatites, hydrothermal veins, and some metamorphic schists and gneisses.
