Oxy-schorl (IMA 2011-011), ideally Na(Fe<sup>2+sup><sub>2sub>Al)Al<sub>6sub>Si<sub>6sub>O1<sub>8sub>(BO<sub>3sub>)<sub>3sub>(OH)<sub>3sub>O, a new mineral species of the tourmaline supergroup, is described. In Zlatá Idka, Slovak Republic (type locality), fan-shaped aggregates of greenish black acicular crystals ranging up to 2 cm in size, forming aggregates up to 3.5 cm thick were found in extensively metasomatically altered metarhyolite pyroclastics with Qtz+Ab+Ms. In Přibyslavice, Czech Republic (co-type locality), abundant brownish black subhedral, columnar crystals of oxy-schorl, up to 1 cm in size, arranged in thin layers, or irregular clusters up to 5 cm in diameter, occur in a foliated muscovite-tourmaline orthogneiss associated with Kfs+Ab+Qtz+Ms+Bt+Grt. Oxy-schorl from both localities has a Mohs hardness of 7 with no observable cleavage and parting. The measured and calculated densities are 3.17(2) and 3.208 g/cm<sup>3sup> (Zlatá Idka) and 3.19(1) and 3.198 g/cm<sup>3sup> (Přibyslavice), respectively. In plane-polarized light, oxy-schorl is pleochroic; O = green to bluish-green, E = pale yellowish to nearly colorless (Zlatá Idka) and O = dark grayish-green, E = pale brown (Přibyslavice), uniaxial negative, ω = 1.663(2), ɛ = 1.641(2) (Zlatá Idka) and ω = 1.662(2), <span class="sc">ɛspan> = 1.637(2) (Přibyslavice). Oxy-schorl is trigonal, space group R3m, Z = 3, a = 15.916(3) Å, c = 7.107(1) Å, V = 1559.1(4) Å<sup>3sup> (Zlatá Idka) and a = 15.985(1) Å, c = 7.154(1) Å, V = 1583.1(2) Å<sup>3sup> (Přibyslavice). The composition (average of 5 electron microprobe analyses from Zlatá Idka and 5 from Přibyslavice) is (in wt%): SiO<sub>2sub> 33.85 (34.57), TiO<sub>2sub> <0.05 (0.72), Al<sub>2sub>O<sub>3sub> 39.08 (33.55), Fe<sub>2sub>O<sub>3sub> not determined (0.61), FeO 11.59 (13.07), MnO <0.06 (0.10), MgO 0.04 (0.74), CaO 0.30 (0.09), Na<sub>2sub>O 1.67 (1.76), K<sub>2sub>O <0.02 (0.03), F 0.26 (0.56), Cl 0.01 (<0.01), B<sub>2sub>O<sub>3sub> (calc.) 10.39 (10.11), H<sub>2sub>O (from the crystal-structure refinement) 2.92 (2.72), sum 99.29 (98.41) for Zlatá Idka and Přibyslavice (in parentheses). A combination of EMPA, Mössbauer spectroscopy, and crystal-structure refinement yields empirical formulas (Na<sub>0.591sub>Ca<sub>0.103sub>□<sub>0.306sub>)<sub>∑1.000sub>(Al<sub>1.885sub>Fe<sup>2+sup><sub>1.108sub>Mn<sub>0.005sub>Ti<sub>0.002sub>)<sub>∑3.000sub>(Al<sub>5.428sub>Mg<sub>0.572sub>)<sub>∑6.000sub>(Si<sub>5.506sub>Al<sub>0.494sub>)<sub>∑6.000sub>O<sub>18sub> (BO<sub>3sub>)<sub>3sub>(OH)<sub>3sub>(O<sub>0.625sub>OH<sub>0236sub>F<sub>0.136sub>Cl<sub>0.003sub>)<sub>∑1000sub> for Zlatá Idka, and (Na<sub>0.586sub>Ca<sub>0.017sub>K<sub>0.006□0.391sub>)<sub>∑1.000sub>(Fe<sup>2+sup><sub>1.879sub>Mn<sub>0.015sub> Al<sub>1.013sub>Ti<sub>0.093sub>)<sub>∑3.00sub>(Al<sub>5.732sub>Mg<sub>0.190sub>Fe<sup>3+sup><sub>0.078sub>)<sub>∑6.000sub>(Si<sub>5.944sub>Al<sub>0.056sub>)<sub>∑6.000sub>O<sub>18sub>(BO<sub>3sub>)<sub>3sub>(OH)<sub>3sub>(O<sub>0.579sub>F<sub>0.307sub>OH<sub>0.115sub>)<sub>∑1.000sub> for Přibyslavice. Oxy-schorl is derived from schorl end-member by the AlOFe<sub>–1sub>(OH)<sub>–1sub> substitution. The studied crystals of oxy-schorl represent two distinct ordering mechanisms: disorder of R<sup>2+sup> and R<sup>3+sup> cations in octahedral sites and all O ordered in the W site (Zlatá Idka), and R<sup>2+sup> and R<sup>3+sup> cations ordered in the Y and Z sites and O disordered in the V and W sites (Přibyslavice).
