Oxy-schorl, Na(Fe2+2Al)Al6Si6O18(BO3)3(OH)3O, a new mineral from Zlata Idka, Slovak Republic and Pribyslavice, Czech Republic (original) (raw)
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European Journal of Mineralogy, 2015
Fluor-schorl, NaFe 2+ 3 Al 6 Si 6 O 18 (BO 3) 3 (OH) 3 F, is a new mineral species of the tourmaline supergroup from alluvial tin deposits near Steinberg, Zschorlau, Erzgebirge (Saxonian Ore Mountains), Saxony, Germany, and from pegmatites near Grasstein (area from Mittewald to Sachsenklemme), Trentino, South Tyrol, Italy. Fluor-schorl was formed as a pneumatolytic phase and in high-temperature hydrothermal veins in granitic pegmatites. Crystals are black (pale brownish to pale greyish-bluish, if ,0.3 mm in diameter) with a bluish-white streak. Fluor-schorl is brittle and has a Mohs hardness of 7; it is non-fluorescent, has no observable parting and a poor/indistinct cleavage parallel to {0001}. It has a calculated density of $3.23 g/cm 3. In plane-polarized light, it is pleochroic, O ¼ brown to grey-brown (Zschorlau), blue (Grasstein), E ¼ pale grey-brown (Zschorlau), cream (Grasstein). Fluorschorl is uniaxial negative, o ¼ 1.660(2)-1.661(2), e ¼ 1.636(2)-1.637(2). The mineral is rhombohedral, space group R3m, a ¼ 16.005(2), c ¼ 7.176(1) Å , V ¼ 1591.9(4) Å 3 (Zschorlau), a ¼ 15.995(1), c ¼ 7.166(1) Å , V ¼ 1587.7(9) Å 3 (Grasstein), Z ¼ 3. The eight strongest observed X-ray diffraction lines in the powder pattern [d in Å (I)hkl] are: 2.584(100)(051), 3.469(99)(012), 2.959(83)(122), 2.044(80)(152), 4.234(40)(211), 4.005(39)(220), 6.382(37)(101), 1.454(36)(514) (Grasstein). Analyses by a combination of electron microprobe, secondary-ion mass spectrometry (SIMS), Mössbauer spectroscopic data and crystal-structure refinement result in the structural formulae X (Na 0.82 K 0.01 Ca 0.01 & 0.16) Y (Fe 2+ 2.30 Al 0.38 Mg 0.23 Li 0.03 Mn 2+ 0.02 Zn 0.01 & 0.03) AE3.00 Z W [(OH) 0.6 F 0.4 ]. The investigated tourmalines from the Erzgebirge show that there exists a complete fluor-schorl-schorl solid-solution series. For all studied tourmaline samples, a distinct inverse correlation was observed between the X-O2 distance (which reflects the mean ionic radius of the X-site occupants) and the F content (r 2 ¼ 0.92). A strong positive correlation was found to exist between the F content and the ,Y-O. distance (r 2 ¼ 0.93). This correlation indicates that Fe 2+-rich tourmalines from the investigated localities clearly tend to have a F-rich or F-dominant composition. A further strong positive correlation (r 2 ¼ 0.82) exists between the refined F content and the Y-W (F,OH) distance, and the latter may be used to quickly estimate the F content.
Mineralogical Magazine, 2018
ABSTRACTYellowish dravitic tourmaline (dominated by the oxy-dravite component) associated with secondary fluor-dravite/fluor-schorl and dravite/schorl tourmalines was found in a quartz vein cropping out in the eastern part of the Karkonosze Mountains range, SW Poland. The crystal structure of this tourmaline was refined to an R1 value of 1.85% based on single-crystal data, and the chemical composition was determined by electron-microprobe analysis. The tourmaline, a representative of the alkali-tourmaline group, has the structural formula: (Na0.75Ca0.12□0.13)Σ1(Mg1.93Al0.95Ti0.06${\rm Fe}_{{\rm 0}{\rm. 04}}^{{\rm 2 +}} $ V0.01)Σ3(Al5.38Mg0.62)Σ6B3Si6O27(OH)3(O0.46OH0.33F0.21)Σ1, and is characterized by an extremely high Mg/(Mg + Fe) ratio of 0.97–0.99, the WO2– content that reaches 0.59 apfu resulting in a local predominance of the oxy-dravitic component and Mg–Al disorder on the octahedral Y and Z sites of the order of 0.64 apfu. This disordering results in an increasing <Z–O>...
Minerals, 2022
Discreditation of the monoclinic tourmaline mineral species luinaite-(OH), ideally (Na,▯)(Fe2+,Mg)3Al6(BO3)3Si6O18(OH)4 was approved by the IMA-CNMNC (proposal 21-L) and is described. We analyzed two luinaite-(OH) samples: one from the type locality Cleveland tin mine, Luina, Waratah, Tasmania, Australia, and the other from Blue Mountain Saddle (Bald Hornet Claim), North Bend, King County, Washington, DC, USA. Biaxial (−) crystals representative of the studied samples were spectroscopically (Mössbauer, polarized Fourier transform infrared, optical absorption spectroscopy), chemically (nuclear microprobe analysis and electron microprobe analysis), and structurally characterized (single-crystal X-ray diffraction). Results show the occurrence of a triclinic structure for the studied luinaite-(OH) samples, which differs only in terms of a slight structural distortion from typical trigonal tourmaline structure (the topology of the structure is retained). As a result, following the IMA-CN...
Oxyphlogopite K(Mg,Ti,Fe)3(Si,Al)4O102: A new mineral species of the mica group
Geology of Ore Deposits, 2011
Oxyphlogopite is a new mica group mineral with the idealized formula K(Mg,Ti,Fe) 3 [(Si,Al) 4 O 10 ](O,F) 2. The holotype material came from a basalt quarry at Mount Rothenberg near Mendig at the Eifel volcanic complex in Rhineland Palatinate, Germany. The mineral occurs as crystals up to 4 × 4 × 0.2 mm in size encrusting cavity walls in alkali basalt. The associated minerals are nepheline, plagioclase, sanidine, augite, diopside, and magnetite. Its color is dark brown, its streak is brown, and its lus ter is vitreous. D meas = 3.06(1) g/cm 3 (flotation in heavy liquids), and D calc = 3.086 g/cm 3. The IR spectrun does not contain bands of OH groups. Oxyphlogopite is biaxial (negative); α = 1.625(3), β = 1.668(1), and γ = 1.669(1); and 2V meas = 16(2)° and 2V calc = 17°. The dispersion is strong; r < v. The pleochroism is medium; X > Y > Z (brown to dark brown). The chemical composition is as follows (electron microprobe, mean of 5 point analyses, wt %; the ranges are given in parentheses; the H 2 O was determined using the Ali marin method; the Fe 2+ / Fe 3+ was determined with X ray emission spectroscopy): Na 2 O 0.99 (0.89-1.12),