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Scandio-winchite, the first natural Sc-dominant amphibole-supergroup mineral, has been discovered in a granitic pegmatite that crops out in close association with rodingite-like calc-silicate rocks and metasomatized granitic bodies in a serpentinite quarry at a Jordanów Śląski village near Sobótka, ~30 km south of Wrocław, Lower Silesia, SW Poland. It occurs as an isolated subhedral crystal, with the size of ~20 × 8 μm in planar section, and as three polycrystalline aggregates, up to 50 μm across, composed of needle-shaped crystals dominated by {110}. It is present within chlorite aggregates that supposedly represent remnants of partly recrystallized xenoliths of the blackwall chlorite schists and is in quartz-feldspar portions of the pegmatite adjoining such xenolithic assemblages. Owing to the scarcity of the material and the exceptionally small size of the crystals, the color, streak, and optical properties could not be measured. By analogy with other amphiboles, scandio-winchite has a vitreous luster, brittle tenacity, and a Mohs hardness of ~5½. The mineral shows an uneven fracture and {110} perfect cleavage, with an angle of ~56° between cleavage planes. The density calculated from the empirical formula and refined unit-cell parameters is 3.026 g/cm3. The holotype crystal is composed of (in wt%): 55.88 SiO2, 0.11 TiO2, 0.53 Al2O3, 9.22 Sc2O3, 0.44 MnO, 8.89 FeO, 12.77 MgO, 5.71 CaO, 4.12 Na2O, 0.17 K2O, and 2.09 H 2 O c a l c (+) ; total 99.93. The composition normalized on the basis of 22 O2− + 2 (OH)− ions corresponds to the empirical formula A(□0.966K0.031Na0.003)Σ1B(Na1.132Ca0.868)Σ2 C (M g 2.704 F e 1.055 2 + M n 0.053 S c 1.140 A l 0.023 T i 0.012 ) Σ 4.987 T (S i 7.935 A l 0.065 ) Σ 8.000 O 22 (O H) 2 , simplified formula (□,K)(Na,Ca)2[(Mg,Fe)4Sc](Si8O22)(OH)2, and the ideal formula □(NaCa)(Mg4Sc)(Si8O22)(OH)2. The crystal structure was refined in the monoclinic system, space-group symmetry C2/m, with R1 index of 6.57%. Its unit-cell parameters are: a = 9.864(2) Å, b = 18.163(3) Å, c = 5.3053(16) Å, β = 104.41(3)°, V = 920.6(4) Å3; Z = 2, and the a:b:c ratio is 0.5431:1:0.2921. The crystal-structure refinement indicates almost exclusively Si-occupied T sites, the M4 sites occupied by nearly equal amounts of Na and Ca, M1 and M3 sites by divalent Mg + Fe cations, and M2 filled in equal proportions by divalent cations and Sc. These results, along with the dominant vacancy at the A site, univocally indicate that the mineral corresponds to a M2Sc-analog of winchite. Scandio-winchite is most likely a secondary phase of metasomatic origin related to the evolution of the country rocks and partial alteration of the blackwall chlorite schists xenolith induced by the pegmatitic melt and associated fluids. [ABSTRACT FROM AUTHOR]

Scandian actinolite evolving to scandio-winchite (up to 5.45 wt% Sc2O3) has been found in chloritedominant xenoliths incorporated into marginal portion of a granitic pegmatite. The pegmatite intruded a blackwall schist zone developed around rodingite-type rocks exposed in a serpentinite quarry at Jordanów Śląski near Sobótka, ~30 km south of Wrocław, Lower Silesia, Poland. The amphiboles form irregular overgrowths around cascandite and represent a complex solid-solution series among actinolite and scandio-winchite end-members, with a trace contribution of "scandio-magnesio-hornblende." Structural studies of a scandian actinolite crystal with composition A[□0.995(2)K0.005(2)]Σ1B[Na0.24(5)Ca1.73(4)]Σ1.98(1) C M g 3.74 (7) F e 0.90 (3) 2 + M n 0.04 (1) S c 0.26 (3) A l 0.05 (1) Σ 4.99 (1) T S i 7.98 (2) A l 0.02 (2) Σ 8.00 O 22 (O H) 2 revealed monoclinic C2/m structure with unit-cell parameters a = 9.8517(3), b = 18.0881(6), c = 5.28501(18) Å, β = 104.809(4)°, in which scandium is located solely at the CM2 site. Scandian amphiboles are uncommon in geological environments, and invite comments on the origin of the observed Sc enrichment in the amphibole structure. Textural appearance of the chlorite-cascandite-amphibole clusters suggests that the formation of the amphiboles is related to the evolution of the country rocks followed by partial alteration of blackwall schist xenoliths by pegmatite-forming melt. [ABSTRACT FROM AUTHOR]

Two tourmaline samples occurring in quartz veinlets, which cross-cut an amphibolite body at the Budniki camp near the Kowary town in the south-west part of the Karkonosze Mountains, SW Poland, were studied through microprobe and single crystal X-ray diffraction. Samples were extracted from core and rim regions of crystals with concentric zoning. Chemical and structural data revealed that the core tourmaline is characterised by a dravite–oxy-dravite composition, with the formula: X(Na0.82Ca0.07K0.01Sr0.01□0.09)Σ1Y(Mg1.73Fe2+0.81Fe3+0.41Ti0.04V0.01)Σ3Z(Al5.85Fe3+0.15)Σ6(TSi6O18)(BO3)3(OH)3W(OH0.50O0.50)Σ1 and unit cell parameters a = 15.97377(14) Å and c = 7.22644(7) Å. The rim part of the crystals has a magnesio-lucchesiite composition, described by the formula: X(Ca0.49Na0.41K0.04Sr0.02□0.04)Σ1Y(Mg1.87Fe2+0.95Ti0.15Fe3+0.02V0.02)Σ3Z(Al5.49Fe3+0.51)Σ6(BO3)3(TSi6O18)(OH)3W(O0.81F0.18OH0.01)Σ1 with unit cell parameters a = 15.9863(3) Å and c = 7.22426(15) Å. Both tourmalines show similar refined populations at the Y and Z sites: Y[(Fe2+0.810Mg0.680)Σ1.490(Al1.044Fe3+0.413V0.009)Σ1.465Ti0.045]Σ3Z(Al4.806Mg1.042Fe3+0.152)Σ6 (dravite–oxy-dravite), and Y[(Fe2+0.945Mg0.750)Σ1.695(Al0.737Fe3+0.404V0.018)Σ1.159Ti0.146]Σ3Z(Al4.749Mg1.115Fe3+0.137)Σ6 (magnesio-lucchesiite), with a comparable Mg/(Mg + Fe) ratio of ~0.54–0.56, oxidation of Fe expressed as Fe3+/Fetotal ratio ~0.36–0.41, and trace components such as Ti, Sr, V, Cr, Ni and Co. The geological history of the eastern Karkonosze region in the Kowary vicinity indicates that both tourmalines crystallised from B-bearing metamorphic fluids mobilised by Variscan prograde metamorphism from the protoliths of the Velká Upá mica schists that host the Budniki amphibolite. The fluids migrated into the tectonised amphibolite enriched in Ti, V, Cr, Ni and Co, and mineralised the fractures within it through deposition of soluble species in the form of quartz–tourmaline veinlets. Magnesio-lucchesiite crystallised in an early retrogression stage, probably from Ca- and F-bearing fluids secondary enriched in B by the dissolution of dravite–oxy-dravite. The Budniki camp is, in addition to the type and co-type magnesio-lucchesiite localities, the third documented occurrence of the species worldwide. [ABSTRACT FROM AUTHOR]

The crystallochemical evolution of tourmalines from a quartz vein cutting an amphiboliticinsert within mica schists in the eastern part of metamorphic envelope of the KarkonoszeGranite massif close to the Kowary town in Lower Silesia, Poland (NE part of Moldanubian)was studied in detail. The amphibolite was formed from a mixed magmatic-sedimentaryprotoliths (connected with pre-Variscian bimodal volcanism products like basic lavas andbasic tuffs), which underwent regional Variscan metamorphism under MP-MT conditions,and then were modified by contact metamorphism induced by the intrusion of the KarkonoszeGranite pluton [1]. The primary tourmaline occurs as multi-zoned crystals of alkali group (XNa+K > XCa> □X) with varying relationship between WOH and WO, corresponding respectively toMg-bearing schorl or oxy-schorl. It evolves to a calcic tourmaline (XCa > XNa+K> □X), probably with predominance of WO over WOH (fluorine is absent in bothtourmaline types) of uvite type. The octahedral occupants are dominated by Al, Mg and Fe2+in both tourmaline types, although Al is not sufficient to fill the Z site completely (5.5 < Al <6 apfu). As in tourmalines of uvite type Al deficiency is commonly completed by Mg, weconsider, at the lack of structure data, that in our tourmalines the Y sites are dominantlyoccupied by Fe2+. As a result, the main Y, Z and W-site occupants suggest that thecalcic tourmaline could correspond to oxy-feruvite species unknown to date. TheMg/Mg+Fe ratio reaches the values from 0.64 in the schorl-type tourmaline to 0.48 in theuvitic tourmaline. The increased TiO2 amount locally reaches up to 1.58 wt.%,although it is without any accordance in relation to the first or second tourmalinetype. The main trend of chemical evolution of the tourmalines during the progrademetamorphism is highly connected with amphibolite as their host rock. The increasing role ofCa, Ti and Fe, resulting in the formation of feruvite to possible oxy-feruvite, is probablyrelated to progressive decomposition of plagioclases and associated Ti oxides (ilmenite,rutile) from the host amphibolite during the regional Variscan metamorphism. (Mochnacka etal., 2008). It seems that the formation of the quartz vein containing the tourmalines isconnected with increasing of temperature and fluid activity, the latter, perhaps,released during the contact metamorphism event conducted by Karkonosze Graniteintrusion. Acknowledgment: The study was supported by the National Science Centre (Poland)grant 2017/27/N/ST10/01579 to M.S.. References: [1]Mochnacka, K., Oberc-Dziedzic, T., Mayer, W. and Pieczka, A. 2000. Tiremobilization and sulphide/sulphoarsenide mineralization in amphibolites: effect of graniteintrusion (the Karkonosze-Izera Massif, SW Poland). Geological Quarterly, 52,349–368. [2]Oberc-Dziedzic, T., Kryza, R., Mochnacki, K. and Larionov, A. 2010. Ordovicianpassivecontinental margin magmatism in the Central-European Variscides: U–Pb zircondatafrom the SE part of the Karkonosze-Izera Massif, Sudetes, SW Poland. InternationalJournal of EartSciences (Geologishe Rundschau) 99, 27–46. [ABSTRACT FROM AUTHOR]