Oxy-schorl
Oxy-schorl is an IMA-recognized mineral species in the silicate class, with the chemical formula Na(Fe²⁺₂Al)Al₆(Si₆O₁₈)(BO₃)₃(OH)₃O.
It crystallizes in the hexagonal crystal system (space group R3m). It is a member of the Tourmaline structural group.
Key properties: Mohs hardness 7; specific gravity 3.17–3.19; Pale gray streak; Vitreous luster; optically uniaxial.
IMA symbol Osrl, IMA status: approved, named in 2011.
Hydrothermal fracture fillings in metasomatized rocks (Slovakia); a metasomatized primary magmatic mineral in granite, now foliated orthogneiss (Czech Republic).
It is found associated with Orthoclase perthite, albite, quartz, muscovite, biotite, garnet, apatite, zircon, magnetite, pyrite, ilmenite (Czech Republic).
The prefix oxy indicating a schorl with O2– > OH1– + F1– in the W site and related to end- member schorl by YR2++W(OH) ↔ YAl+WO.