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Oxy-schorl (IMA 2011-011), ideally Na(Fe 2  2+ Al)Al 6 Si 6 O 18 (BO 3 ) 3 (OH) 3 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/cm3 (Zlatá Idka) and 3.19(1) and 3.198 g/cm 3  (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), ε = 1.641(2) (Zlatá Idka) and ω = 1.662(2), ε = 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 3  (Zlatá Idka) and a = 15.985(1) Å, c = 7.154(1) Å, V = 1583.1(2) Å 3  (Přibyslavice). The composition (average of 5 electron microprobe analyses from Zlatá Idka and 5 from Přibyslavice) is (in wt%): SiO 2  33.85 (34.57), TiO 2  &lt;0.05 (0.72), Al 2 O 3  39.08 (33.55), Fe 2 O 3  not determined (0.61), FeO 11.59 (13.07), MnO &lt;0.06 (0.10), MgO 0.04 (0.74), CaO 0.30 (0.09), Na 2 O 1.67 (1.76), K 2 O &lt;0.02 (0.03), F 0.26 (0.56), Cl 0.01 (&lt;0.01), B 2 O 3  (calc.) 10.39 (10.11), H 2 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 0.591 Ca 0.103 □ 0.306 ) Σ1.000 (Al 1.885 Fe 2+   1.108 Mn 0.005 Ti 0.002 ) Σ3.000 (Al 5.428 Mg 0.572 ) Σ6.000 (Si 5.506 Al 0.494 ) Σ6.000 O 18  (BO 3 ) 3 (OH) 3 (O 0.625 OH 0.236 F 0.136 Cl 0.003 ) Σ1.000  for Zlatá Idka, and (Na 0.586 Ca 0.017 K 0.006 □ 0.391 ) Σ1.000 (Fe 2+  1.879 Mn 0.015  Al 1.013 Ti 0.093 ) Σ3.00 (Al 5.732 Mg 0.190 Fe 3+  0.078 ) Σ6.000 (Si 5.944 Al 0.056 ) Σ6.000 O 18 (BO 3 ) 3 (OH) 3 (O 0.579 F 0.307 OH 0.115 ) Σ1000  for Přibyslavice. Oxy-schorl is derived from schorl end-member by the AlOFe -1 (OH) -1  substitution. The studied crystals of oxy-schorl represent two distinct ordering mechanisms: disorder of R 2+  and R 3+  cations in octahedral sites and all O ordered in the W site (Zlatá Idka), and R 2+  and R 3+  cations ordered in the Y and Z sites and O disordered in the V and W sites (Přibyslavice).

Oxy-schorl, Na(Fe 2 2+ Al)Al 6 Si 6 O 18 (BO 3 ) 3 (OH) 3 O, a new mineral from Zlatá Idka, Slovak Republic and Přibyslavice, Czech Republic