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Replacement textures involving four scandium silicate minerals in the Heftetjern granitic pegmatite, Norway
Abstract
Four late-hydrothermal scandium silicate minerals, related by replacement textures, were studied by EMPA and SIMS. Textural evidence shows that early-formed thortveitite is broken up by bazzite and scandian milarite, which seem to occur in equilibrium. Thortveitite is also partly replaced by kristiansenite. The two steps of alteration involve first the introduction of fluids rich in Be, K, Ca and Cs to form bazzite and milarite and then Ca and Sn for the formation of kristiansenite. Addition of water accompanies both steps. Thortveitite is unusually rich in SnO2 (up to 5.67 wt. %). The amount of Sn is balanced by Mn according to the substitution scheme 2Sc(3+) double left right arrow Sn4+ + Mn2+. Bazzite is strongly zoned with respect to Cs and has up to 8.55 wt. % Cs2O. The alkali content in the structural channels is balanced by Fe2+ and Mn2+ substituting for Sc. Scandian milarite is close to the end-member formula K(CaSc)Be-3(Si12O30) with nearly all Al replaced by Be and half of the Ca atoms by Sc. Kristiansenite is very near to the ideal formula Ca2ScSn(Si2O7)(Si2O6OH).
... The granite is hosted in part by a basement gneiss (1520 to 1500 Ma) and in part by the Rjukan metasedimentary-metavolcanic group of the Telemark Supracrustal Suite, deposited 1300 to 1200 Ma ago (Dons 1960) and metamorphosed to the low-pressure epidote-amphibolite to amphibolite facies at about 1060 Ma (Mitchell 1967, Oftedahl 1980, Bergstøl & Juve 1988). The pegmatite population, generally confi ned to the Rjukan group, is mostly barren, but the more evolved pegmatites contain a (Li, Be, Sc, Y>Ce, Sn, Ti, Nb, Ta)-bearing assemblage of accessory minerals (Bergstøl & Juve 1988, Juve & Bergstøl 1990, Kristiansen 2003, Raade & Kristiansen 2002, Raade & Bernhard 2003, Raade et al. 2004. The granite-cumpegmatite suite was characterized as a member of the mixed NYF-LCT family, generated by contamination of an A-type NYF magma by LCT components assimilated from the host supracrustal rocks (Černý 1991). ...
... The material was later forwarded to the Mineralogy-Crystallography group at the University of Manitoba, where the data for the new-mineral-species proposal were collected. A second sample of oftedalite -Sc-rich-milarite was found by RK in 2001 as a product of replacement involving four Sc-silicate minerals (Raade & Bernhard 2003, Raade et al. 2004. ...
... Oftedalite -Sc-rich-milarite was found in two samples: one containing green tourmaline, yttrian milarite, bazzite and an unidentifi ed micaceous mineral, the other containing thortveitite, bazzite, kristiansenite and bertrandite. The specimen of Sc-rich milarite described here comes from the fi rst assemblage; additional compositional data are available from the second specimen, as mentioned below (sample H03/01b of Raade et al. 2004). ...
Oftedalite, ideally (Sc,Ca,Mn2+)(2) K (Be,Al)(3) Si12O30, is a new mineral species from the Heftetjern granitic pegmatite, northwest of the small parish of Tordal, southern Norway. It occurs as short prismatic crystals up to 100 mu m in diameter, frequently with very thin crystals of Sc-free milarite up to similar to 10-20 mu m across in parallel orientation on the (001) faces, or as a product of replacement with other Sc-bearing minerals. Oftedalite - Sc-rich milarite is greyish white with a colorless streak and vitreous luster; it does not fluoresce under ultraviolet light. It has a poor cleavage parallel to {001}, a Mohs hardness of 6, is brittle with a conchoidal fracture, and has a calculated density of 2.614 g/cm(3). It is uniaxial negative, with epsilon 1.553, omega 1.556 (both +/-0.002), and is nonpleochroic. It is hexagonal, space group P6/mcc, a 10.097(1), c 13.991(2) angstrom, V 1235.3(6) angstrom(3), Z = 2. The strongest seven lines in the X-ray powder-diffraction pattern [d in angstrom(I)(hkl)] are: 3.229(10)(104, 211), 4.097(7)(112), 5.044(5)(110), 3.504(5)(004), 7.012(4)(002), 1.836(4)(412), 1.751(4)(008, 500), and 2.735(3) (204). A chemical analysis by electron microprobe gave SiO2 73.32, Al2O3 0.47, Sc2O3 6.77, Y2O3 0.36, FeO 0.26, MnO 1.32, CaO 4.49, K2O 4.71, BeO (calc.) 7.4 1, sum 99.11 wt.%; the Be content was determined as (3 - Al) apfu. The resulting empirical formula on the basis of 30 atoms of oxygen is (Sc0.96Ca0.79Mn0.182+Fe0.042+)(Sigma 2.00) K-0.98 (Be2.91Al0.09)(Sigma 3.0) Si-11.98 O-30. The crystal structure of Sc-rich milarite, (Sc0.84Ca1.03 Mn0.092+Y0.01Fe0.032+)(Sigma 2.00) K (Be2.86Al0.14)(Sigma 3.0) Si12O30)], very close to the ideal composition of oftedalite, was refined to an R index of 6.6% based on 430 observed reflections collected on a four-circle diffractometer with MoK alpha X-radiation and a lK CCD detector. Oftedalite is isostructural with milarite, ideally Ca-A(2) (B)square K-c (T(2))(Be2Al) ((Si12O30)-Si-T(1)) (H2O). The structure consists of a beryllo-aluminosilicate framework of the form (4(2)6(4))(4)(6(4)9(2)) in which the T(1) site is occupied by Si and forms a [Si12O30] cage, and the T(2) site is occupied by (Be + Al) and links the [Si12O30] cages into a framework. The A, B and C sites occur in the interstices of the framework with the following occupancies: A (Sc0.84Ca1.03Mn0.092+Y0.01Fe0.032+); B square; C K-1.00; T(2) (Be2.86Al0.14).
... The occurrence of the two rare Scsilicates bazzite, ideally Be 3 Sc 2 Si 6 O 18 , and thortveitite, (Sc, Y) 2 Si 2 O 7 , defines the pegmatites from Königshain as a particularly important mineralogical site. Similar associations of Sc, Be, and REE minerals with zinnwaldite are scarce, with the Heftetjern pegmatite in Tørdal, Norway (Raade et al. 2004), and the miarolitic pegmatites at Baveno, Italy (Gramaccioli et al. 2004), being the best-known localities. ...
... For instance, it remains unresolved whether the Li-micas are the only Cs-bearing minerals present in the pegmatites. From the minerals accompanying the Li-micas from Königshain, other major potential repositories of Cs are beryl, which may contain up to 11.3 wt % Cs 2 O (Schaller et al. 1962, Evans & Mrose 1968,Černý 1972, and bazzite (8.55 wt % Cs 2 O; Raade et al. 2004). ...
Annite and Fe-rich siderophyllite constitute the rock-forming micas in the late-Variscan composite granite pluton of Königshain, Lausitz, Germany. This multiphase pluton is composed of three fractionated, but not chemically specialized monzogranite types, which contain lithophile elements such as Li, Rb, Cs, Sn, and F in average quantities. Abundant miarolitic pegmatites of the NYF family with a broad diversity of rare minerals occur in the apical part of the pluton. These pegmatitic cavities locally contain di- and trioctahedral micas as well as cation-deficient micas. Trioctahedral micas comprise F-rich manganoan lithian siderophyllite to manganoan zinnwaldite, zinnwaldite, and minor lepidolite. The formula [calculated on the basis of 22 anion valencies and 2(F + OH + Cl)] of the most Mn-rich siderophyllite is (K0.85Rb0.08Na0.04)0.97(Al0.99Li0.91Fe0.51Mn0.42Ti0.01Zn0.01)2.85(Si3.21Al0.79)4O10(F1.80OH0.19Cl0.01)2. This mica constitutes one of the most Mn-rich siderophyllite compositions reported to date. The lithium micas poorer in Mn are distinguished by elevated concentrations of Rb (up to 2.5 wt% Rb2O), Cs (up to 1.2 wt% Cs2O), and F (up to 9.6 wt%). This fluorine content is probably consistent with the maximum possible F occupation of 2 of the (F,OH,Cl)-site. The structural formula of the most Li-rich lepidolite is (K0.83Rb0.07Cs0.03)0.93 (Li1.62Al1.00Fe0.38)3.00(Si3.62Al0.38)4O10(F1.91OH0.09)2. During hydrothermal alteration, lepidolite and zinnwaldite became partially depleted in K, Li, Rb, Cs, and F and gradually transformed into cation-deficient micas (lithian phengite to illite of phengitic affinity).
... These processes were facilitated by fluids exsolved from residual pegmatite melt (e.g., Wang et al., 2009;Buřival and Novák, 2018;Uher et al., 2022) and/or external fluids derived from host rocks or from various external magmatic, hydrothermal, or metamorphic sources (e.g., Novák et al., 2017;Č opjaková et al., 2021;Chládek et al., 2021;Rybnikova et al., 2023). Replacements of large crystals or aggregates by mostly fine-grained mineral assemblages commonly manifest these subsolidus hydrothermal alterations (e.g., Č erný, 2002;Raade et al., 2004;Roda-Robles et al., 2004;Gadas et al., 2016Gadas et al., , 2020 and may provide a valuable information about P-T-X conditions of these secondary processes, chemical composition of acting fluids as well as their sources. ...
... The mineralogy of this pegmatite and the general geology of the area were first described by Bergstøl and Juve (1988), who reported on an unusual occurrence of scandian ixiolite, scandian members of the pyrochlore and microlite groups, and cesian bazzite. The Heftetjern pegmatite is a dike, ~300 m long and 5 to 40 m thick, hosting the zone, less than 10 m long, 3-4 m wide and less than 2 m deep, extremely enriched in Sc and Be minerals (Kristiansen, 2009 (Raade and Erambert, 1999;Raade and Bernhard, 2003;Raade and Kristiansen, 2003;Raade et al., 2002Raade et al., , 2004Cooper et al., 2006;Lussier et al., 2009;Kolitsch et al., 2010;Hawthorne et al., 2014;Miyawaki et al., 2015;Chukanov et al., 2017;Raade, 2020;Steffenssen et al., 2020). Heflikite is a part of this late-stage mineral assemblage. ...
Heflikite, the first Sc-dominant epidote-supergroup mineral, was discovered in two occurrences. The holotype was found in a granitic pegmatite associated with rodingite-like calc-silicate rocks and metasomatised granitic bodies exposed in a serpentinite quarry at Jordanów Śląski near Sobótka, Lower Silesia, SW Poland. The cotype comes from the Heftetjern pegmatite, Tørdal region, Norway. The holotype is composed of (in wt.%): 35.69 SiO2, 0.22 TiO2, 21.98 Al2O3, 6.12 Sc2O3, 0.07 V2O3, 1.10 Fe2O3, 0.11 Y2O3, 1.55 La2O3, 4.05 Ce2O3, 0.31 Pr2O3, 1.53 Nd2O3, 0.40 Sm2O3, 0.11 EuO, 0.56 Gd2O3, 0.14 MnO, 3.56 FeO, 0.16 MgO, 19.16 CaO, and 1.78 H2O(+)calc.; total 98.60. The cotype contains: 34.92 SiO2, 0.44 TiO2, 0.82 SnO2, 19.13 Al2O3, 4.79 Sc2O3, 1.96 Fe2O3, 2.55 La2O3, 7.39 Ce2O3, 0.48 Pr2O3, 0.67 Nd2O3, 0.12 Eu2O3, 0.61 Gd2O3, 0.13 MnO, 5.97 FeO, 17.66 CaO, and 1.73 H2O(+)calc.; total 99.37. The compositions correspond to the following empirical formulae: (Ca1.729Ce0.125La0.048Nd0.046Gd0.016Sm0.012Pr0.010Y0.005Eu2+0.003)Σ1.994 [(Al2.182Sc0.449Fe3+0.070V3+0.005)Σ2.706 (Fe2+0.251Mg0.020Mn0.010)Σ0.281 Ti0.014]Σ3.001(Si3.006O11)O(OH) and (Ca1.644Ce0.235La0.082Nd0.021Gd0.018Pr0.015Eu2+0.004)Σ1.019 [(Al1.958Sc0.362Fe3+0.128)Σ2.448 (Fe2+0.434Mn0.009)Σ0.443 (Ti0.029Sn0.029)Σ 0.058]Σ2.949 (Si3.033O11)O(OH), respectively, and to the ideal formula Ca2(Al2Sc)(Si2O7)(SiO4)O(OH). The crystal structure of the holotype was refined in the monoclinic system with an R1 index of 8.62 %. The crystal-structure refinement indicates exclusively Si occupied T sites, Al occupied M1 and M2 sites, and Ca occupied A1 site. The M3 site is predominantly filled by trivalent cations, mainly Sc3+, with divalent cations (mainly Fe2+) as minor occupants. The A2 site is filled mostly by Ca with minor amounts of REE. The holotype heflikite crystallised from metasomatic fluids that infiltrated a contact between the granitic pegmatite and the surrounding rodingite-type calc-silicate rocks and serpentinites. The fluids that introduced Sc into the pegmatite could have been either hydrothermal or related to low-grade regional metamorphism that postdated the formation of the pegmatite. The cotype heflikite formed during the late-stage hydrothermal crystallisation of the Sc-enriched granitic pegmatite.
... Bazzite (Be 3 Sc 2 Si 6 O 18 ) has been reported in granitic pegmatites from Tørdal in south Norway, which formed during a late stage of pegmatite crystallization (Bergst and Juve 1988). In the Tørdal pegmatites, another two species of complex, Sc-bearing silicates were discovered and named as Kristiansenite (Ca 2 ScSn(Si 2 O 7 )(Si 2 O 6 OH)) and Oftedalite ((Sc,Ca,Mn) 2 K(Be,Al) 3 Si 12 O 30 ) (Raade et al. 2004;Cooper et al. 2006). The hydrous Sc phosphate, kolbeckite (Sc(PO 4 )•2H 2 O), was distinguished in weathered quartz veins within pegmatites from Germany, which might be related to carboniferous granites (Dill et al. 2006). ...
Scandium (Sc) is a dispersed metal in Earth’s lithosphere, with an average abundance of 16 to 22 ppm. In the meantime, it is widely considered as a critical metal because of its paramount significance in scientific research and technical innovation. With surging demands that are not backed-up by current supplies globally, the market price of Sc oxide is astonishingly five times more than the most expensive rare earth oxide of terbium (Tb). Production of Sc is significantly held back due to scarcity of economically viable grades at explorable depths within the crust, compared with other critical metals such as REE, Nb and Ta. Nevertheless, typical high- to intermediate-grade Sc deposits, as compiled in this review, consistently show close relationships to specific magmatic (e.g. ultramafic-mafic and carbonatitic), supergene and hydrothermal processes during Sc enrichment, especially the former two. Known potential Sc deposits are tentatively classified based on their host rocks and metallogeny, including those hosted in the ultramafic-mafic rocks and related laterites, in carbonatite and related laterites, in bauxite residue and processed coals, hydrothermal Sc deposits and Sc deposits related to syenite intrusions, pegmatites or marine sediments. We also discuss the Sc enrichment mechanism and associated tectonics and partition coefficients of Sc among diverse minerals and melts, which reveal the preference of Sc for clinopyroxene, garnet and iron oxides by isomorphic replacement or ion absorption during diverse magmatic and supergene Sc enrichment processes. Lastly, Sc resources in the world-class Bayan Obo deposit are discussed in detail as an illustrative benchmark example, where hydrothermal aegirine may host majority of carbonatite-derived Sc.
... The most important past, current and potential future sources of Sc include: 1) granitic pegmatites of the NYF (Černý and Ercit, 2005) geochemical family (e.g. Pezzotta et al., 2005;Kolitsch et al., 2010;Raade et al., 2004;Guastoni et al., 2012); 2) carbonatites (Amli, 1977;Shimazaki et al., 2008;Kalashnikov et al., 2016); 3) greisens ; 4) Al-laterites (Ochsenkühn-Petropoulou et al., 2002;Wang et al., 2011;Wang and Li, 2020); and 5) Sc-bearing Ni laterites developed on ultramafic rocks (Aiglsperger et al. 2016, Teitler et al., 2019. Other Sc sources include hydrothermal U ores, Fe, Ti and Zr ores and apatite; see Wang et al. (2011) and Wang and Li (2020) for review. ...
Scandium is a metal with specific industrial applications and its importance is expected to grow significantly in future. For its use in high-tech alloys and solid oxide fuel cells it is regarded as a strategic metal. The world-class Li-Sn-W Cínovec/Zinnwald greisen-type deposit contains significant amount of Sc which could be an interesting by-product in anticipated production of Li, Sn and W. We conducted systematic study of Sc abundances and mineralogical controls of its fractionation during magmatic and post-magmatic evolution of the Cínovec granite copula and its greisen deposits. From the main accessory minerals found in (partially to strongly) metasomatized granites, the highest concentrations of Sc2O3 were found in columbite (≤ 3.0 wt.%), zircon (≤ 2.5 wt.%), and Nb-rutile (≤ 0.3 wt.%) which are supplemented by wolframite (≤ 1.0 wt.%), ixiolite (≤ 4.9 wt.%) and cassiterite (≤ 0.3 wt.%) in greisens and quartz-zinnwaldite veins. However, the major Sc-carrier in most rock types and especially in greisens is the common zinnwaldite (typically 40-85 ppm Sc) hosting up to 93% of the total Sc. Younger fluids causing zinnwaldite muscovitization and rare sulfidic overprint were significantly depleted in Sc and caused mobilization of Sc and/or its redistribution into secondary minerals.
... Both kristiansenite [ideally Ca 2 ScSn(Si 2 O 7 )(Si 2 O 6 OH)] and kamphaugite-(Y) [CaY(CO 3 ) 2 (OH)·H 2 O] minerals have been scarcely studied mainly due to the difficulty of finding them because of their small size and, consequently, there are very few specimens located worldwide. Concerning kristiansenite, only located in Heftetjern (Norway), Baveno (Italy), Szklarska Porcba, Lower Silesia (Poland) (up to now), there are only few studies about the description of the crystal structure by X-ray diffraction (XRD) (Ferraris et al. 2001;Raade et al. 2002;Evans et al. 2018) and chemical composition by electron-microprobe analyses (EMPA) and secondary-ion mass spectrometry (SIMS) (Raade et al. 2004;Evans et al. 2018). In turn, kamphaugite-(Y), more abundant than kristiansenite, has been collected in many different granite pegmatite locations involving Norway (Hørtekollen, Buskerud; Høydalen, Telemark; Tangen, Kragerø), Italy (Cala Francese, Sardinia), Kazakhstan, Russia, Hungary, South Africa, Canada, USA, Australia and Spain (La Cabrera area, about 150 km far from Cadalso de los Vidrios). ...
This paper reports on the cathodoluminescence (CL) emission of kamphaugite-(Y) (CaY(CO3)2(OH)·H2O) and kristiansenite [Ca2ScSn(Si2O7)(Si2O6OH)] that display very complex spectra. The carbonate sample, growing in spheres no longer than 3 mm, contains signiicant concentrations of REE giving rise to sharp and narrow wavebands peaked at 312, 486, 546, 574 and 626 nm. These wavebands would be, respectively, associated with the presence of Gd3+ (6P7/2 → 8S7/2 transition), Dy3+ (4F9/2 → 6H15/2), Tb3+ (5D4 → 7F5), Dy3+ (4F9/2 → 6H13/2) and Sm3+ (4G5/2 → 6H7/2). Kristiansenite, appearing as an isolated pseudo-hexagonal pyramidal crystal smaller than 600 μm, hardly has lanthanide elements and the CL emission is composed of broad wavebands peaked at 298 nm (linked to defect-sites caused by the presence of the Na-0.49%), 334 (due to oxygen vacancies and Me–O bonding defects), 422 (–O–O– type defects and/or O2− intrinsic defects), 494 (self-trapped excitons), 578 [Mn2+ giving rise to 4T2(G) → 6A1(S) transition and/or Ti4+/Sn4+ redox reactions] and 654 nm [due to Fe3+ 4T1(G) → 6A1(S) transitions]
... The main accessory minerals are beryl, spessartine, gadolinite-(Y), cassiterite, scandian ixiolite, zircon, monazite-(Ce), Sc-bearing pyrochlore-group minerals, milarite and phenakite. A late mineral assemblage encountered mainly in vugs and fractures comprises bertrandite, triclinic titanite (Lussier et al., 2009), bohseite, bazzite, thortveitite (Raade et al., 2004), helvite, cascandite, scandiobabingtonite (Raade & Erambert, 1999), kristiansenite (Raade et al., 2002), heftetjernite (Kolitsch et al., 2010) and agakhanovite-(Y) (Hawthorne et al., 2014). Most minerals described below occur in vugs in amazonite and quartz and are associated with bertrandite, spessartine, Ce-enriched epidote, zircon, Mn-bearing hellandite-(Y) (Miyawaki et al., 2015), biotite, opal, violet and white yttrian fluorite and remnants of a metamict microlite-group mineral. ...
A hydroxyl-dominant analogue of gadolinite-(Y) (OH-Gad) has been discovered in the Heftetjern granitic pegmatite, Southern Norway, in association with late-stage REE-minerals. The empirical formula based on 10 O apfu is (Y1.285Ca0.55Ce0.07La0.04Nd0.01)1.955Fe2+0.57Be2.02Si1.995O8.48(OH)1.52. The mineral is monoclinic, space group P21/c, a = 4.7514(10), b = 7.5719(16), c = 9.9414(2) Å, = 90.015(4)°, V = 357.663(3) Å3, and Z = 2. Density calculated using the empirical formula is 3.903 g/cm3. The crystal structure was refined to R = 0.0217 for 776 > 2(I). OH-Gad is isostructural with gadolinite-(Y) and it is characterized by the predominance of OH– over O2– at the anionic Ø-site. Refined crystal-chemical formula is (Z = 2): A(Y1.25Ca0.55Ce0.2)X(Fe2+0.570.43)ZBe2TSi2O8Ø[(OH)0.86O0.59(OH)*0.55]. Possible orientation and local environment of hydroxyl group were suggested based on bond-valence sum calculations and geometrical analysis of the crystal structure. The IR spectrum confirms disordering of hydrogen atoms. OH-Gad is seems to be a potentially new mineral – the first simultaneously hydroxyl- and iron-dominant member of gadolinite subgroup. It is a OH-analogue of gadolinite-(Y) and Fe2+-analogue of hingganite-(Y).
... Here, "zinnwaldite" and cassiterite are the most common Li-and Sn-minerals, respectively. The Heftetjern pegmatite is famous for its unique assemblage of Sc-minerals and Sc-bearing minerals, such as the new species kristiansenite (Raade et al. 2002), oftedalite (Cooper et al. 2006), and heftetjernite (Kolitsch et al. 2010), as well as bazzite (Juve & Bergstøl 1990), scandiobabingtonite and cascandite (Raade & Erambert 1999), and thortveitite (Kristiansen 2009); the latter is also intimately intergrown with three of the former (Raade et al. 2004). According to the classification of Černý (1992), the Tørdal pegmatites are of mixed LCT-NYF (Li, Cs, Ta -Nb, Y, F) affinity. ...
Mn-bearing hellandite-(Y) occurs as pinkish yellow granular crystals (up to sub mm) in the Sc-rich granite pegmatite at Heftetjern, Tørdal, Telemark, Norway. Associated minerals are quartz, albite, Sc- and Ce-bearing epidote, hingganite-(Y), and an undetermined Ca-bearing hingganite-related mineral. Electron microprobe analyses give an empirical formula as Ca1.34Mn1.07Y2.75Ce0.02Nd0.02Sm0.01Gd0.01Dy0.05Er0.05Yb0.15Al0.94Fe0.08Si3.99B4.33O22.00 (OH)2.00 on the basis of Al+Fe+Si = 5 and 24 anions per formula unit. The lattice parameters were refined from diffraction data obtained using a Gandolfi camera with an imaging plate and Ni filtered CuKα; a 18.693(17), b 4.651(3), c 10.178(7) A, β = 111.37(6)°, V 824.1(10) A3. The crystal structure was refined from single-crystal XRD data obtained with a CCD-diffractometer and graphite-monochromated MoKα. The refinement with anisotropic atomic displacement parameters converged to R1 = 0.0269 for 1567 reflections [I > 2σ(I)] and 0.0318 for all 1768 reflections, resulting in the structural formula M3(Ca0.56Mn0.44)2M4(Y0.43 Ca0.23Ln0.140.20)2M2(Y0.94Ln0.06)2M1(Al0.92Fe0.08)Si4B4O21.21 (OH)2.79. In this hellandite-(Y), Mn2+ replaces Ca2+ at the M3 site and there is a significant vacancy at the M4 site. The T site is vacant, and, instead, the O5 position is occupied by (OH)-.
... Pikes Peak, Colorado). The Kracovice pegmatite is a typical example the mixed NYF/LCT family and it is similar to the pegmatites at Tørdal, Norway (Bergstøl and Juve 1988; Raade et al. 1993Raade et al. , 2004. ...
The fieldtrip guidebook contains information about localities which were visited during pre-conference fieldtrip in the Czech Republic and during the post-conference fieldtrip in Poland along with the major geological backround and development of the related areas . Also a few pictures of macroscopic samples from the individual localitites are included.
... Pikes Peak, Colorado). The Kracovice pegmatite is a typical example the mixed NYF/LCT family and it is similar to the pegmatites at Tørdal, Norway (Bergstøl and Juve 1988; Raade et al. 1993Raade et al. , 2004. ...
The fieldtrip guidebook contains information about localities which were visited during pre-conference fieldtrip in the Czech Republic and during the post-conference fieldtrip in Poland along with the major geological backround and development of the related areas . Also a few pictures of macroscopic samples from the individual localitites are included.
... Other contributors to the increase in diversity are granitic pegmatites, a zinc deposit, metamorphic rocks and skarns, and hydrothermal supergene alteration. Minerals in granitic pegmatites include secondary Sc-Be minerals bazzite and oftedalite from the Heftetjern pegmatite, renowned for its diversity in Sc minerals (e.g., Raade et al. 2004;Bergstøl and Juve 1988;Juve and Bergstøl 1990). The Heftejern pegmatite is related to the Tørdal granite (Bergstøl and Juve 1988;Cooper et al. 2006), which is coeval with 967 ± 4 Ma (U-Pb zircon) post-orogenic Vrådal granite in Telemark, Norway (Bergstøl and Juve 1988;Andersen et al. 2007). ...
Beryllium is a quintessential upper crustal element, being enriched in the upper crust by a factor of 30 relative to primitive mantle, 2.1 vs. 0.07 ppm. Most of the 112 minerals with Be as an essential element are found in granitic pegmatites and alkalic rocks or in hydrothermal deposits associated with volcanic and shallow-level plutonic rocks and skarns. Because of the extensive differentiation needed to enrich rocks sufficiently in beryllium for beryllium minerals to form, these minerals are relative latecomers in the geologic record: the oldest known is beryl in pegmatites associated with the Sinceni pluton, Swaziland (3000 Ma). In general, beryllium mineral diversity reflects the diversity in the chemical elements available for incorporation in the minerals and increases with the passage of geologic time. Furthermore, the increase is episodic; that is, steep increases at specific times are separated by longer time intervals with little or no increase in diversity. Nonetheless, a closer examination of the record suggests that at about 1700 Ma, the rate of increase in diversity decreases and eventually levels off at ~35 species formed in a given 50 Ma time interval between 1125 and 475 Ma, then increases to 39 species at 125 Ma (except for four spikes), before dropping off to ~30 species for the last 100 Ma. These features appear to reflect several trends at work: (1) diversifications at 2475, 1775, and 525 Ma, which are associated with highly fractionated rare-element granitic pegmatites and with skarns at Långban and similar deposits in the Bergslagen ore region of central Sweden, and which are inferred to correspond to the collisional phases of the supercontinents Kenorland, Nuna, and Gondwana, respectively; (2) diversification at 1175 Ma due to the rich assemblage of beryllium minerals in the Ilímaussaq peralkaline complex, Gardar Province, West Greenland, in an extensional environment; (3) diversification at 275 Ma, which is largely attributable to granitic pegmatites (Appalachian Mountains, U.S.A., and Urals, Russia) and the Larvik alkalic complex, Norway, but nonetheless related to continental collision; and (4) limited exhumation of environments where beryllium minerals could have formed in the last 100 Ma. That the maximum diversity of Be minerals in any one geologic environment could be finite is suggested by the marked slowing of the increase in the number of species formed in a given 50 Ma time interval, whereas the drop off at 100 Ma could be due to 100 Myr being too short a time interval to exhume the deep-seated occurrences where many Be minerals had formed. The relative roles of chance vs. necessity in complex evolving systems has been a matter of considerable debate, one equally applicable to what extent the temporal distribution of beryllium minerals is a matter of contingency. On the one hand, the appearance of the most abundant Be minerals, such as beryl and phenakite, early in the history of Be mineralization appears to be a deterministic aspect since these minerals only require the abundant cations Al and Si and crystallize at relatively low concentrations of Be in aqueous solution or granitic magmas. On the other hand, it could be argued that the very existence of most other Be minerals, as well as the temporal sequence of their appearance, is a matter of chance since 55 of the 112 approved Be minerals are known from a single locality and many of these phases require an unusual combination of relatively rare elements. Consequently, we cannot exclude the possibility that other equally rare and thus contingent potential Be minerals await discovery in as yet unexposed subsurface deposits on Earth, and we suggest that details of Be mineral evolution on other Earth-like planets could differ significantly from those on Earth.
... The scandian garnets described here belong to a new type of skarn mineralization. Known silicate scandium minerals (thortveitite, bazzite, jervisite, cascandite, scandiobabingtonite, kristiansenite, scandiomilarite) and the oxide "scandioixiolite" are found only in pegmatites (Mellini et al. 1982;Orlandi et al. 1998;Bergstøl and Juve 1988;Černy et al. 2000;Raade et al. 2002Raade et al. , 2004Gramaccioli et al. 2004). Scandium phosphates (kolbeckite, juonnite, pretulite) crystallize under low-temperature conditions (Bernhard et al. 1998(Bernhard et al. , 2001Liferovich et al. 1998). ...
Garnet from an aposkarn achtarandite-bearing rodingite-like rock in Sakha-Yakutia, Russia, has a Sc content close to 6 wt%
Sc2O3 (~0.45 apfu). The scandian garnet is a relict mineral from a high-temperature, shallow-level melilite skarn. Structural and
electron microprobe data for a crystal of the scandian garnet with cell parameter a = 12.331(1) Å, Ia3̅d allows refinement of the structural formula (Ca2.97Mg0.02Y0.01)∑3(Fe3+ 0.663Zr0.584Ti4+ 0.294Sc0.153Cr0.152Mg0.094Fe2+ 0.04Hf0.008V0.003)∑2(Si1.898Al0.420Ti4+0.359 Fe3+ 0.323)∑3O12. Investigation of the composition of many of the scandian garnets reveals the existence of a solid-solution between kimzeyite-schorlomite
Ca3(Zr,Ti)2(Al,Fe)2SiO12 and the scandium analog of andradite Ca3Sc2Si3O12. This is the first report of a natural scandian garnet.
... The occurrence of Sc minerals in the Heftetjern pegmatite was first recognized by Bergstøl and Juve (1988), who reported scandian ixiolite, 'scandium microlite' (Jambor, 1990) and other scandian members of the pyrochlore group. Recent investigation of the pegmatite has revealed a unique assemblage of Sc minerals, with seven minerals containing Sc as an essential element: cesian bazzite (Juve and Bergstøl, 1990), scandiobabingtonite, cascandite (Raade and Erambert, 1999), thortveitite (Kristiansen, 2003;Raade et al., 2004) and the new minerals kristiansenite (Raade et al., 2002), oftedalite (Cooper et al., 2006;Kristiansen, 2005) and heftetjernite (Kolitsch et al., 2009;Kristiansen, 2009). There are~60 mineral species in the Heftetjern pegmatite (Raade and Kristiansen, 2000a,b;Raade and Segalstad, 2003, RK pers. ...
Two crystals from a sample of titanite from the Heftetjern granitic pegmatite, Tørdal, southern Norway, were extracted for structure analysis and shown to have triclinic symmetry. Unit-cell parameters are as follows: a = 7.0696(4) Å, b = 8.7167(5) Å, c = 6.5695(3) Å, α = 89.7372(11)°, = 113.7607(10)°, = 90.2929(13)°, V = 370.52(6) Å3 for one crystal and a = 7.0612(5) Å, b = 8.7102(6) Å, c = 6.5628(4) Å, α = 89.7804(16)°, = 113.7713(13)°, = 90.2502(16)°, V = 369.39(7) Å3 for the other. The interaxial angles α and deviate from the value of 90° required for monoclinic symmetry by ∼200–250 standard deviations. The single-crystal X-ray intensities were averaged in both monoclinic and triclinic Laue symmetries, giving R(merge) values of ∼14% and ∼1.3% respectively. For both crystals, more than 50 reflections with I > 3I violated the criterion for the presence of the a-glide required for monoclinic A2/a symmetry. Both crystals were refined in the space group A1 with Z = 4, and final R1 indices are 4.4% and 4.7% (wR2 = 8.4 and 8.9%) respectively. The composition of one crystal was determined by electron microprobe analysis: Ca[Ti0.623Ta0.105Nb0.018Al0.137Fe3+0.046Sn4+0.083]Σ=1.012(SiO4)O. The characteristic corner-sharing [MO5] chains of identical octahedra observed in monoclinic titanite become chains of alternating M(1) and M(2) octahedra of different size, with the stronger X-ray scattering constituents concentrated at the M(2) site. Short-range bond-valence considerations suggest that the M cations will order as Al–O–Ta in adjacent octahedra, and when present in sufficient amounts, will couple along the chain to break long-range monoclinic symmetry.
... A recent set of analyses of thortveitite, associated with xenotime-(Y), from this occurrence, have high SnO 2 contents (Guastoni and Nestola, 2010). Elevated SnO 2 contents in thortveitite have also been reported by Raade et al. (2004); they reach 5.6 wt.% in crystals from miarolitic cavities in the Heftetjern granitic pegmatite in Norway. ...
Xenotime-(Y), (Y,REE)PO4, and thortveitite, (Sc,Y)(2)Si2O7, in a miarolitic cavity in a niobium, yttrium, fluorine (NYF) granitic pegmatite at Baveno, Verbania, Southern Alps, Italy, were investigated by electron microprobe analysis and single-crystal X-ray diffraction. Fluorine has an important role as a complexing agent for Y and REEs in supercritical pegmatitic fluids; annite-siderophyllite and chamosite are the most likely sources of the Y and REEs. The thortveitite from Baveno contains up to 3.20 wt.% SnO2, an unusually high Sn content. Xenotime-(Y) is enriched in Gd in comparison to other Alpine xenotimes. Quantitative chemical data and measurements of the lattice parameters show that a higher scandium content results in a smaller unit-cell volume in thortveitite. The substitution of REEs for Y up to similar to 20 mol.% has little effect on the unit cell of xenotime-(Y). The textures of xenotime-(Y) and thortveitite provide information about the dissolution and crystallization processes in the miarolitic cavity.
Helvine-group minerals from two granitic pegmatites have disparate compositions, from nearly pure helvine (Ågskardet, northern Norway; Devonian) to helvine close to ternary compositions (Heftetjern, southern Norway; Precambrian). Metagranite from Høgtuva (northern Norway; Precambrian with Caledonian metamorphic overprint) contains Zn-rich danalite. The Ågskardet helvine contains up to 0.46 wt.% SnO2, and the Heftetjern ternary helvine shows a maximum of 1.74 wt.% Sc2O3. Helvine minerals were also analyzed from three occurrences connected to peralkaline granite (ekerite) of the Permian Oslo Rift. Nearly pure genthelvite (99.19 mol.%) occurs in miarolitic cavities at Gjerdingselva. Two mineralogically different granitic pegmatites derived from the same ekerite pluton in the southern part of the Oslo Rift show quite distinct helvine compositions, from nearly continuous solid solution between helvine and genthelvite in crystals with oscillatory zonation (Rundemyr) to solid solutions midway between danalite and genthelvite (Bakstevalåsen). The Rundemyr crystals have a maximum SnO2 content of 1.28 wt.%. The incorporation of minor elements (Ca, Mg, Al, Sn, Sc) in helvine-group minerals is discussed with emphasis on their chalcophilicity characteristics. For stereochemical reasons, Sn in helvine minerals must be tetravalent, even if Sn2+ is more chalcophile than Sn4+.
Three distinct types (A, B and C) of secondary pretulite (ScPO4) were found in a single andalusite-diaspore nodule from the quartz core of the pegmatite dyke No. 3, Dolní Bory, Czech Republic. Primary crystallization of the nodule containing pretulite precursors - Sc, Y, U, P-rich zircon and Sc,W-rich ixiolite - proceeded at T ≤ 410 °C and P ≤ 2 kbar. Subsequent subsolidus hydrothermal alteration at T ≈ 350–300 °C transformed part of the andalusite to pyrophyllite, and triggered complete dissolution of Sc, Y, U, P-rich zircon I. In-situ reprecipitation produced Y, U-depleted zircon II with common inclusions of xenotime II and pretulite A (0.88–0.92 apfu Sc, 0.04–0.07 apfu Zr, < 0.03 apfu Y). During the same process recrystallization of Sc, W-rich ixiolite produced heterogeneous pretulite B (0.21–0.89 apfu Sc, 0.09–0.78 apfu Zr, ≤ 0.07 apfu Y). The origin of pretulite C (almost ideal ScPO4) closely associated with pyrophyllite replacing andalusite and distant from the potential Sc-precursors is explained by the separation of Sc from other HFSE present in the original precursors, which were immobile probably due to absence of suitable strong ligands in the fluids. Saturation of any Sc-dominant mineral (except thortveitite, Sc2Si2O7) is almost never achieved during primary magmatic crystallization due to the extremely high compatibility of Sc; consequently, the processes of hydrothermal alteration of Sc-enriched precursors and the selective mobilization and fractionation of Sc from other HFSE are important for the formation of scandium minerals.
We report herein a new find of kristiansenite from a pocket in an intragranite pegmatite from Cadalso de los Vidrios, near Madrid, Spain. This specimen of a late hydrothermal scandium silicate has been studied by Environmental Scanning Electron Microscopy with Energy Dispersive Spectrometry probe (ESEM-EDS), Micro-Raman Spectrometry and ESEM-Cathodoluminescence (ESEM-CL), all of them non-destructive techniques. The sample is a single perfect pyramidal monocrystal found in a small cavity less than one mm across. The experimental chemical, molecular and spectral luminescent information was later compared with the type specimen from Norway and the second ¿nd, at Baveno, Italy. Our Raman spectrum matches the spectrum of the Norwegian specimen, with minor variation in the intensity of the peaks; the chemical composition recorded by EDS also shows minor variations. In addition, the CL spectrum displays several narrow peaks, probably associated with REE in Ca positions. The geochemical framework of this new locality, with pegmatite pockets in A-type granites rich in Sc-bearing minerals and other REE, have many similarities with those of Norway and Italy.
An intragranitic, euxenite-type NYF pegmatite, Kozichovice II, derived from the ultrapotassic orogenic Trebic syenogranite pluton, contains pale green prismatic crystals of primary beryl I, up to 3 cm long, arranged in radial aggregates. They are typically enclosed in massive quartz at the contact with albite or K-feldspar. Beryl I is locally altered to the secondary mineral assemblage beryl II + bavenite + bazzite + smectite. Electron-microprobe and LA-ICP-MS data yielded: slight indications of heterogeneity in beryl I, with high Na (0.20-0.32 apfu), Mg (0.24-0.38 apfu), moderate Fe(tot) (0.06-0.14 apfu), Sc (<= 0.06 apfu, 0.05-0.68 wt.% Sc(2)O(3)), Cs (0.01-0.15 apfu, 0.23-3.65 wt.% Cs(2)O), and very low Li (<= 80 ppm); secondary beryl II with high Na (0.24-0.34 apfu), low Fe(tot) (0.03-0.05 apfu), Sc (<= 0.02 apfu, <= 0.22 wt.% Sc(2)O(3)), and Cs (<= 0.005 apfu; <= 0.14 wt.% Cs(2)O); bazzite with high Na (0.38-0.48 apfu), Mg (0.41-0.64 apfu), Fe(tot) (0.09-0.33 apfu), Sc (1.13-1.22 apfu, 12.79-13.80 wt.% Sc(2)O(3)), and moderate Ca (0.10-0.16 apfu, 0.91-1.53 wt.% CaO). Low-temperature measurements (25 K) of (57)Fe Mossbauer spectra of beryl I yielded: (O,CH)Fe(2+) similar to 80%, (T)Fe(2+) similar to 10% and (O)Fe(3+) similar to 10%. The substitutions: (1) (CH)square (O)R(3+) = (CH)R(+) (O)R(2+) where R(+) = Na, Cs, K, Rb; R(2+) = Mg, Fe(2+), Mn, Ca; R(3+) = Al, Sc, Fe(3+), and (2) (CH)square 2(O)R(3+) = (CH)Ca 2(O)R(2+) [or modified (CH)square (2)OR(3+) = (CH)(Ca,Fe(2+))2(O)R(2+)] were revealed. A sum of Na + K + Rb + Cs > 0.5 apfu found in bazzite from Kozichovice, Kazakhstan and Tordal, Telemark, Norway, suggests the existence of new phases related to bazzite via the substitution (1) with the general formula R(+)Be(3)R(3+)R(2+)Si(6)O(18) and idealized formulas Na(+)Be(3)ScMg(2+)Si(6)O(18) (Kozichovice) and Na(+)Be(3)ScFe(2+)Si(6)O(18) (Kazakhstan, Norway). Low Fe/(Fe + Mg) values, in the range 0.14-0.29 in beryl I, are similar to those in the other Fe, Mg minerals (biotite, tourmaline, amphibole) from the pegmatites of the Trebic pluton. The (Na, Mg, Fe)-enriched crystals of beryl examined are similar to various, but mostly non-pegmatitic environments rather than to NYF pegmatites, and support a rather unique bulk-composition and compositional evolution of minerals from granitic pegmatites of the Trebic pluton. The assemblage of secondary minerals after beryl I, including common bavenite and elevated Ca in bazzite, suggest a high activity of Ca in the late fluids, which is perhaps enhanced by very low contents of P and F in pegmatites of the Trebic pluton. We suggest a temperature slightly below 250-350 degrees C and neutral to slightly alkaline conditions for the formation of the secondary assemblage beryl II + bavenite + bazzite + smectite.
Heftetjernite,ideally ScTaO4, is a new scandium mineral from the Heftetjern pegmatite, T0ℝ, Telemark, Norway. In the type specimen, it occurs as minute, elongate tabular, very dark brown crystals in a single small void in albite. Other associated minerals are fluorite, muscovite, altered milarite, a metamict, dark greyish brown mineral of the pyrochlore-microlite group, and an unidentified, orange-brown, tabular, nearly X-ray amorphous Ti-Y-Ta-Nb-mineral. Electron-microprobe analysis yielded the empirical formula (Sc0.64Sn0.13Mn0.12Fe0.08Ti 0.06)σ1.03(Ta0.69Nb0.30) σ0.99O4 which clearly demonstrates the charge-balanced substitution scheme 2Sc3+ = (Sn,Ti)4+ + (Mn,Fe)2+. Themineral crystallises in the wolframite structure type, with space group P2/c and a= 4.784(1), b= 5.693(1), c = 5.120(1) Å , β = 91.15(3)-B, V = 139.42(5) Å 3 (Z = 2). A synthetic equivalent is known. Strongest lines in the calculated X-ray powder diffraction pattern of heftetjernite are [d in Å (I) (hkl)]: 3.000 (100) (11-1), 2.9570 (97) (111), 3.662 (53) (110), 2.4877 (34) (02-1), 4.783 (33) (100), 3.807 (32) (01-1). The crystal structure was refined to R(F)= 1.39%from single-crystal X-ray diffraction data (293 K). It is based on two types of edge-sharing, distorted octahedra occupied predominantly by Sc and Ta, respectively. Heftetjernite is translucent to transparent, with a dark brownish (with a reddish hue) streak and adamantine lustre. It is brittle, has a perfect {010} cleavage, irregular fracture and a Mohs hardness estimated to be around 4.5 by comparison to ferberite; Dx = 6.44 g/ cm3 (from crystal-structure analysis). Optically, the mineral is biaxial with an unknown optical sign, weakly pleochroic (yellowish brown with a reddish tint to reddish brown), with no observable dispersion. A mean refractive index of 2.23 was calculated from the Gladstone-Dale relationship using the X-ray density. Heftetjernite is named after its type locality. The mineral is compared with synthetic ScTaO 4, ScNbO4, iwashiroite-(Y) and formanite-(Y) (both nominally YTaO4), and some comments are made on the relation to Sc-bearing ixiolite.
An investigation on Sn–W and W deposits and associated granites in the Erzgebirge region, central Kazakhstan, Mongolian Altai, and central Mongolia reveals anomalously high Sc contents up to several thousands of parts per million in wolframite and cassiterite from Sn–W deposits in the eastern Erzgebirge; even though whole-rock samples of granites from these localities have low Sc contents typical of high-silica granitic rocks.It is possible to trace the distribution of Sc in rocks and veins using data on accessory and ore minerals enriched in Sc (columbite, rutile, cassiterite, wolframite, zircon, scheelite, and mica). There are no indications for an enrichment of Sc during the magmatic evolution of the granite intrusions. Magmatic fractionation causes rather low Sc contents in evolved granites. On the other hand, Sc enrichment in zircon found in these rocks is clearly related to processes of secondary alteration leading to high U, Ca, and Fe besides Sc enrichment in the mineral. Enhanced Sc contents were also found in whole-rock samples from the greisen.The occurrence of Sc-rich wolframite and cassiterite is mainly restricted to endocontact orebodies (greisen and veins). Outside the rare metal-bearing granites, the Sc content in wolframite drops off if host rocks are formed by schist and gneiss. Correlation between Sc and Nb concentrations in wolframite found in endocontact orebodies also disappears in the exocontact veins except if the vein system provides a focused fluid flow.Sc enrichment in Sn–W mineralisation is accompanied by strong Y/Sc, Y/Yb, and Th/U fractionation in Sc-bearing minerals as indicated by trace-element contents in wolframite and scheelite. Y/Sc ratios in wolframite below 0.1 are typical of Sn deposits. It is suggested that certain conditions of complexation, pH, and Eh in F-rich fluids are necessary prerequisites for Sc enrichment and deposition. Our results hint for a Sc input into the ore-forming system by an external F-rich fluid carrying also U and heavy REE and possibly derived from a mantle-related source. Although whole-rock samples of rare metal-bearing topaz granite have low Sc contents, the related Sn–W ores may represent an interesting source for Sc extraction because of their enrichment in Sc.
Economic geology is a mixtum compositum of all geoscientific disciplines focused on one goal, finding new mineral depsosits and enhancing their exploitation. The keystones of this mixtum compositum are geology and mineralogy whose studies are centered around the emplacement of the ore body and the development of its minerals and rocks. In the present study, mineralogy and geology act as x- and y-coordinates of a classification chart of mineral resources called the “chessboard” (or “spreadsheet”) classification scheme. Magmatic and sedimentary lithologies together with tectonic structures (1-D/pipes, 2-D/veins) are plotted along the x-axis in the header of the spreadsheet diagram representing the columns in this chart diagram. 63 commodity groups, encompassing minerals and elements are plotted along the y-axis, forming the lines of the spreadsheet. These commodities are subjected to a tripartite subdivision into ore minerals, industrial minerals/rocks and gemstones/ornamental stones.
Pezzottaite, ideally Cs(Be2Li)Al2Si6O18, is a new gem mineral that is the Cs,Li-rich member of the beryl group. It was discovered in November 2002 in a granitic pegmatite near Ambatovita in central Madagascar. Only a few dozen kilograms of gem rough were mined, and the deposit appears nearly exhausted. The limited number of transparent faceted stones and cat's-eye cabochons that have been cut usually show a deep purplish pink color. Pezzottaite is distinguished from beryl by its higher refractive indices (typically n(o)=1.615-1.619 and n(e)=1.607-1.610) and specific gravity values (typically 3.09-3.11). In addition, the new mineral's infrared and Raman spectra, as well as its X-ray diffraction pattern, are distinctive, while the visible spectrum recorded with the spectrophotometer is similar to that of morganite. The color is probably caused by radiation-induced color centers involving Mn3+.
The characteristics of an end-member formula are defined as follows: (1) the chemical formula must be fixed no variable chemical components are possible (2) the end-member formula must be compatible with the crystal structure of the mineral (or putative mineral) (3) the chemical composition at each site in the crystal structure must be fixed an end-member formula may have two types of cation or anion (in a fixed ratio) at one site in the structure if required for electroneutrality: two cations or anions at more than one site are not allowed. Combining these characteristics of end-member formulae with aspects of their crystal structures can lead to unambiguous definition of end-member compositions of complex minerals, and can give considerable insight into coupled heterovalent substitutions. Several examples are given, The end-member formula of the tourmaline-group mineral povondraite was originally written as Na Fe-3(3+) Fe-6(3+) (Si-6 O-18) (BO3)(3) (O,OH)(4), whereas the correct end-member formula is Na Fe-3(3+) (Fe-4(3+) Mg-2) (Si-6 O-18) (BO3)(3) (OH)(3) O. The yttrium-rich milarite described by Cerny et al. (1991) is shown to be a new mineral of the milarite group, with the end-member formula K (CaY) [Be-3 (Si-12 O-30)]. There are seven accredited ([4])(Li,Zn)-bearing minerals of the milarite group, and there has been some ambiguity over the end-member compositions of darapiosite, dusmatovite and sogdianite end-member formulae for these minerals are unambiguously defined with the approach used here. The complex Be-bearing borosilicate mineral hyalotekite has been somewhat elusive with regard to unambiguous definition of its solid-solution behavior. The ideal formula of Christy et al. (1998) can be resolved into two distinct end-member formulae: ( 1) Ba-4 Ca-2 Si-8 (BeB) (Si)(2) O-28 F, and (2) Ba-4 Ca-2 Si-8 (B-2) (SiB) O-28 F; note that one end-member has essential Be and the other end-member does not. Thus the competing views on whether hyalotekite is a Be mineral or not are both correct, and there are two distinct minerals buried in the chemical compositional data for hyalotekite. "Makarochkinite" is a non-accredited phase described by Yakubovich et al. (1990) that has been identified as identical to hogtuvaite by Grauch et al. (1994). Application of the approach developed here shows that. according to the published chemical data. "makarochkinite" and hogtuvaite have distinct end-member formulae. Ca-2 (Fe-4(2+) Fe3+ Ti) (Si-4 Be Al) O-20 and Ca-2 (Fe-4(2+) Fe-2(3+)) (Si-5 Be) O-20, respectively. These examples show that the very simple approach developed here, using the characteristics of an end-member formula with aspects of the crystal structure, can simply and easily resolve many quite complicated problems in mineral chemistry.
The structure of the new disilicate kristiansenite, Ca2ScSn(Si2O7)(Si2O 6OH), has been solved and refined from a crystal polysynthetically twinned by metric merohedry. The Bravais lattice is mC, with parameters a = 10.028(1), b = 8.408(1), c = 13.339(2) Å, a = 90.01(1), β = 109.10(1), γ = 90-00(1)°, but the space-group type is Cl (Z = 4). The twin law is m', and the two components of the twin have nearly identical volumes: as a consequence, the Laue group of the twin is practically 2/m. By taking into account the twinning, an anisotropic refinement of the structure in Cl converged to R1 = 0.0242 for 259 refined parameters and 4862 observed reflections. The effects of the twinning by metric merohedry and of the volume ratio of the components on the symmetry of the diffraction pattern are discussed. The triclinic structure approximates within about 0.1 Å the monoclinic symmetry, the lower symmetry resulting mainly from cation ordering. Kristiansenite represents a new type of silicate structure and the first known case with the presence of protonated and normal disilicate groups at the same time. The disilicate groups and the other polyhedra centred on cations lie on different alternating (101) planes.
Kristiansenite occurs as a late hydrothermal mineral in vugs in an amazonite pegmatite at Heftetjern, Tørdal, Telemark, Norway.
Tapering crystals, rarely up to 2 mm long, are colourless, white, or slightly yellowish. The mineral has the ideal composition
Ca2ScSn(Si2O7)(Si2O6OH) and is triclinic C1 with cell parameters a = 10.028(1), b = 8.408(1), c = 13.339(2) Å, α = 90.01(1), β = 109.10(1), γ = 90.00(1)°, V = 1062.7(3) Å3 (Z = 4). It has a monoclinic cell within ∼ 0.1 Å and is polysynthetically twinned on {010} by metric merohedry. The strongest
reflections in the X-ray powder pattern are [d in Å, (I
obs), (hkl)]: 5.18 (53) (1–11), 3.146 (100) (004), 3.089 (63) (−222), 2.901 (19) (221), 2.595 (34) (222), 2.142 (17) (−3–31). The Mohs’
hardness is 5½–6; Dcalc. = 3.64 g/cm3; only a mean refractive index of 1.74 could be measured. Scandium enrichment in the Heftetjern pegmatite and the crystal
chemistry of scandium are briefly discussed.
Backscatter images reveal an intergrowth of the two pyroxenoid minerals scandiobabingtonite and cascandite in separate areas exceeding 100 μm in length. Formation of the two minerals appears to be co-eval. The empirical formula of scandiobabingtonite is Ca1.94(Fe2+0.74Mn0.23Mg 0.03)Σ1.00(Sc0.93Fe3+0.05)Σ0.98Si5.06O14(OH) and that of cascandite is Ca1.00(Sc0.81Fe2+0.18Mn 0.04Mg0.01)Σ1.04Si3.03O 8(OH). Compositions between the two extremes would seem to indicate areas with numerous chain periodicity faults.
Summary Bazzite, Be3Sc2Si6O18, the scandium analogue of beryl, is a rare accessory mineral together with ixiolite and pyrochlore of the cleavelandite-amazonite pegmatites at Heftetjern, Tordal, Telemark, Norway. Chemical investigation shows that it contains ca. 3 weight % Cs20. It is, therefore, a caesian bazzite.
A SIMS procedure for Li, Be, and B quantification in silicates has been developed using the empirical approach of working curves via calibration with standards. Medium- to high-energy secondary ions have been used to reduce matrix effects affecting especially Li/Si ionization and to improve measurement reproducibility with respect to low-energy ion analysis for Li, Be, and B. In the case of Be, there has been evidence for a possible reduction of matrix effects, whereas in the case of B, matrix effects have been evidenced to be rather low at any ion energy, and in such a case, the application of a voltage offset has been useful only to improve measurement reproducibility. Positive ions of the isotopes Li-7, Be-9, B-11, and Si-30 (assumed as the matrix reference isotope), having emission kinetic energies ranging from approximately 75 to 125 eV, have been monitored using an ion microprobe Cameca IMS 4F. The calibration curves hold over extended concentration ranges from ppm to percent level by weight for light elements and silica contents ranging from a few percent to more than 80% by weight. Precision and accuracy of the method are generally estimated as better than +/-20% relative at the ppm level and better than +/-10% relative for element abundances of tens of ppm for Be and B. As for Li, the whole uncertainty in the proposed SIMS procedure is evaluated at about +/-20% (28% for lead crystal glasses). These results have important implications for more extensive applications of SIMS as a 'routine'' microanalytical and bulk technique for the quantification of Li, Be, and B in silicate minerals and rocks.
In Trdal granite pegmatite veins cut through a volcano-sedimentary sequence which overlies an older, gneissic basement and younger granite from which they originate. Positive co-variations of scandium, lithium, beryllium and tin, which were documented through a recent prospecting program for tin, indicate a possible enrichment of scandium and tin during the passage of the pegmatitic material through the volcanic sedimentary sequence. A description is given of scandium-rich ixiolite, (Ta,Nb,Sc,Sn,Fe,Mn,Ti)2O4 in association with pyrochlore, (Ca,Sc,Y,Sn,U)2(Ta,Nb,Ti)2O6(O,OH,F) and bazzite, Be3Sc2Si6O18 from a cleavelandite-amazonite pegmatite occurring as a part of a larger network of granitic pegmatite veins. Alteration from ixiolite to pyrochlore appears as a late magmatic-hydrothermal event.In Trdal durchschneiden Granit-pegmatitische Gnge eine vulkano-sedimentre Abfolge, die ber einem lteren Gneis-Basement und einem jngeren Granit, von dem die Gnge stammen, liegt. Positive Kovariation von Scandium, Lithium, Beryllium und Zinn, die sich im Zuge eines Prospektionsprogrammes auf Zinn ergaben, deuten auf eine mgliche Anreicherung von Scandium und Zinn whrend des Aufstieges pegmatitischer Phasen durch die vulkano-sedimentre Abfolge hin. Ein Scandium-reicher Ixiolit in Assoziation mit Pyrochlor und Bazzit wird beschrieben, der aus einem Clea-velandit-Amazonit-Pegmatit stammt. Der Pegmatit bildet einen Teil eines greren Netzwerkes von granit-pegmatischen Gngen. Eine Alteration von Ixiolit zu Pyrochlor tritt als sptmagmatisch-hydrothermales Ereignis auf.
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