Tourmaline - schorl x dravite Pikarec Czech Republic nice specimens with nice fully terminated tops — Photo: AdamStejskal · CC BY 4.0
Dravite
Also known as: Brown tourmaline.
The magnesium end-member of the tourmaline group — typically brown to black, common in metamorphic rocks.
Intro adapted from Wikipedia (CC BY-SA).
Dravite is an IMA-recognized mineral species in the silicate class, with the chemical formula NaMg₃Al₆(Si₆O₁₈)(BO₃)₃(OH)₃(OH).
It crystallizes in the hexagonal crystal system (space group R3m). It is a member of the Tourmaline structural group.
Key properties: Mohs hardness 7.5; specific gravity 3.03–3.18; typically brown or black or yellow; Light brown, white streak; Vitreous to resinous luster; optically uniaxial.
IMA symbol Drv, grandfathered status — known before the IMA’s founding, named in 1884.
is commonly found in metamorphosed limestones or mafic igneous rocks with metasomatically introduced boron; rarely in pegmatites; as authigenic overgrowths in sedimentary rocks.
It is found associated with Quartz, calcite, dolomite, epidote, microcline, albite, muscovite, fluorite, titanite.
The name refers to the district along the Drava (Drave) River in Austria and Slovenia.
Collections: Collector Favorites.