R. Miyawaki, Koichi Momma, S. Matsubara, T. Sano, M. Shigeoka, H. Horiuchi
{"title":"Hydroxykenopyrochlore, (□,Ce,Ba)2(Nb,Ti)2O6(OH,F), a new member of the pyrochlore group from Araxá, Minas Gerais, Brazil","authors":"R. Miyawaki, Koichi Momma, S. Matsubara, T. Sano, M. Shigeoka, H. Horiuchi","doi":"10.3749/CANMIN.2000094","DOIUrl":"https://doi.org/10.3749/CANMIN.2000094","url":null,"abstract":"","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45982434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Owen P. Missen, M. Back, S. Mills, A. C. Roberts, Y. Lepage, W. Pinch, J. A. Mandarino
Keystoneite (IMA87–049) is a tellurite mineral from the Keystone mine, Magnolia District, Boulder County, Colorado, USA. In this paper the first full description of keystoneite is presented. Keystoneite is the Ni2+ analogue of zemannite and has the ideal zemannite-like formula of Mg0.5Ni2+Fe3+(Te4+O3)3·4H2O. The chemical composition via electron-probe micro-analysis (in wt.%; standard deviations in brackets) is Na2O 0.3 (0.2), K2O 0.1 (0.0), MgO 4.3 (0.3), Mn2O3 1.1 (0.7), Fe2O3 5.1 (1.2), NiO 12.7 (1.7), and TeO2 65.5 (0.7). H2O was determined by TGA analysis, giving 15(3) wt.% H2O, however, H2O from the structural determination gave 10.0 wt.%, the latter giving an analytical total of 99.1 wt.%. Keystoneite crystallizes in the non-centrosymmetric space group P63. The six strongest observed powder-diffraction lines [d,Å(I)(hkl)] are 8.12(90)(100), 4.05(80)(200), 2.952(50)(112), 2.838(50)(121,211), 2.774(100)(202), and 1.720(60)(204). The unit-cell parameters determined from single-crystal X-ray diffraction are a = 9.3667(5) Å, c = 7.6173(3) Å, V = 578.77(6) Å3, and Z = 2. Keystoneite was first identified from a specimen of “ferrotellurite”, a mineral with the reported formula Fe2+Te6+O4. The discreditation of “ferrotellurite” has been accepted by the IMA-CNMNC, Proposal 19-G, as no material corresponding to a phase remotely similar to Fe2+Te6+O4 was found on any historical samples labelled as containing “ferrotellurite”.
{"title":"Crystal Chemistry of Zemannite-Type Structures: III. Keystoneite, the Ni2+-Analogue of Zemannite, and Ferrotellurite Discredited","authors":"Owen P. Missen, M. Back, S. Mills, A. C. Roberts, Y. Lepage, W. Pinch, J. A. Mandarino","doi":"10.3749/CANMIN.2000009","DOIUrl":"https://doi.org/10.3749/CANMIN.2000009","url":null,"abstract":"\u0000 Keystoneite (IMA87–049) is a tellurite mineral from the Keystone mine, Magnolia District, Boulder County, Colorado, USA. In this paper the first full description of keystoneite is presented. Keystoneite is the Ni2+ analogue of zemannite and has the ideal zemannite-like formula of Mg0.5Ni2+Fe3+(Te4+O3)3·4H2O. The chemical composition via electron-probe micro-analysis (in wt.%; standard deviations in brackets) is Na2O 0.3 (0.2), K2O 0.1 (0.0), MgO 4.3 (0.3), Mn2O3 1.1 (0.7), Fe2O3 5.1 (1.2), NiO 12.7 (1.7), and TeO2 65.5 (0.7). H2O was determined by TGA analysis, giving 15(3) wt.% H2O, however, H2O from the structural determination gave 10.0 wt.%, the latter giving an analytical total of 99.1 wt.%. Keystoneite crystallizes in the non-centrosymmetric space group P63. The six strongest observed powder-diffraction lines [d,Å(I)(hkl)] are 8.12(90)(100), 4.05(80)(200), 2.952(50)(112), 2.838(50)(121,211), 2.774(100)(202), and 1.720(60)(204). The unit-cell parameters determined from single-crystal X-ray diffraction are a = 9.3667(5) Å, c = 7.6173(3) Å, V = 578.77(6) Å3, and Z = 2. Keystoneite was first identified from a specimen of “ferrotellurite”, a mineral with the reported formula Fe2+Te6+O4. The discreditation of “ferrotellurite” has been accepted by the IMA-CNMNC, Proposal 19-G, as no material corresponding to a phase remotely similar to Fe2+Te6+O4 was found on any historical samples labelled as containing “ferrotellurite”.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47039294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Infinite chains of edge-sharing octahedra occur as fundamental building blocks (FBBs) in the structures of several hundred mineral species. Such chains consist of a backbone of octahedra to which decorating polyhedra may be attached. The general, stoichiometric formula of such chains may be written as c[MATxФz] where M is any octahedrally coordinated cation, T is any cation coordinated by a decoration polyhedron (regardless of coordination geometry), Ф is any possible ligand [O2–, (OH)–, (H2O), Cl–, or F–], and c indicates the configuration of backbone octahedra. In the minerals in which they occur, these types of chains will commonly (though not exclusively) form part of the structural unit (i.e., the strongly bonded part) of a mineral. Hence, investigating the topology, configuration, and arrangement of such chains may yield fundamental insights into the stability of minerals in which they occur. A discussion of the topological variability of chains is presented here, along with the formulae necessary for their characterization. It is shown that many aspects of chain topology can be efficiently communicated by a pair of values with the form ([x], [Bopqrst]), where [x] summarizes the symmetry operations necessary to characterize the configuration of backbone octahedra, B indicates the length of the topological repeat, and o through t indicate the number of individual decorations (related to B). A methodology for developing finite graphical representations for infinite chains is presented in detail, showing that for any given chain, a single, irreducible finite graph exists that contains all topological information. Such a graph, however, can correspond to multiple chain topologies, highlighting the importance of geometrical isomerism. The utility of the graphical approach in facilitating the development of a hierarchy of chains and chain-bearing structures is also discussed.
{"title":"Structure Topology and Graphical Representation of Decorated and Undecorated Chains of Edge-Sharing Octahedra","authors":"A. Lussier, F. Hawthorne","doi":"10.3749/CANMIN.2000061","DOIUrl":"https://doi.org/10.3749/CANMIN.2000061","url":null,"abstract":"\u0000 Infinite chains of edge-sharing octahedra occur as fundamental building blocks (FBBs) in the structures of several hundred mineral species. Such chains consist of a backbone of octahedra to which decorating polyhedra may be attached. The general, stoichiometric formula of such chains may be written as c[MATxФz] where M is any octahedrally coordinated cation, T is any cation coordinated by a decoration polyhedron (regardless of coordination geometry), Ф is any possible ligand [O2–, (OH)–, (H2O), Cl–, or F–], and c indicates the configuration of backbone octahedra. In the minerals in which they occur, these types of chains will commonly (though not exclusively) form part of the structural unit (i.e., the strongly bonded part) of a mineral. Hence, investigating the topology, configuration, and arrangement of such chains may yield fundamental insights into the stability of minerals in which they occur. A discussion of the topological variability of chains is presented here, along with the formulae necessary for their characterization. It is shown that many aspects of chain topology can be efficiently communicated by a pair of values with the form ([x], [Bopqrst]), where [x] summarizes the symmetry operations necessary to characterize the configuration of backbone octahedra, B indicates the length of the topological repeat, and o through t indicate the number of individual decorations (related to B). A methodology for developing finite graphical representations for infinite chains is presented in detail, showing that for any given chain, a single, irreducible finite graph exists that contains all topological information. Such a graph, however, can correspond to multiple chain topologies, highlighting the importance of geometrical isomerism. The utility of the graphical approach in facilitating the development of a hierarchy of chains and chain-bearing structures is also discussed.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42570799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hexiong Yang, X. Gu, B. Cairncross, R. Downs, S. Evans
Two new mineral species, taniajacoite and strontioruizite, ideally SrCaMn2Si4O11(OH)4 2H2O and Sr2Mn2 Si4O11(OH)4 2H2O, respectively, have been identified from the N’Chwaning III mine, Kalahari manganese field, South Africa. Both minerals occur as brown radiating groups or aggregates of acicular or prismatic crystals, with individual crystals up to 0.15 3 0.04 3 0.02 mm for taniajacoite and 1.3 3 0.2 3 0.2 mm for strontioruizite. Minerals associated with taniajacoite include sugilite, aegirine, pectolite, richterite, potassic-ferri-leakeite, and lipuite, whereas those associated with strontioruizite include sugilite, potassic-magnesio-arfvedsonite, and lipuite. Both taniajacoite and strontioruizite are brown in transmitted light, transparent with very light brown streak and vitreous luster. They are brittle and have a Mohs hardness of 5–5.5; cleavage is good on {010} and no parting or twinning is observed macroscopically. The measured and calculated densities are 3.05(2) and 3.09 g/cm, respectively, for taniajacoite and 3.20(2) and 3.16 g/cm for strontioruizite. Optically, both taniajacoite and strontioruizite are biaxial (–), with a1⁄4 1.686(2), b1⁄4 1.729(2), c1⁄4 1.746(2) (white light), 2V (meas.)1⁄4 63.7(5)8, 2V (calc.)1⁄4 62.58 for the former and a1⁄4 1.692(2), b1⁄4 1.734(2), c1⁄4 1.747(2) (white light), 2V (meas.)1⁄4 59.1(5)8, 2V (calc.)1⁄4 56.68 for the latter. The calculated compatibility index based on the empirical formula is 0.008 for taniajacoite and 0.015 for strontioruizite. An electron microprobe analysis yielded an empirical formula (based on 17 O apfu) of Sr(Ca0.81Sr0.19)R1.00(Mn 3þ 1.90Fe 3þ 0.15 Al0.01)R2.06Si3.96O11(OH)4 2H2O for taniajacoite and (Sr1.61Ca0.42)R2.03(Mn1.95Fe0.05)R2.00Si3.98O11(OH)4 2H2O for strontioruizite. Taniajacoite and strontioruizite are isostructural with ruizite. Strontioruizite, like ruizite, is monoclinic with space group C2 and unit-cell parameters a 1⁄4 9.1575(4), b 1⁄4 6.2857(4), c 1⁄4 12.0431(6) Å, b 1⁄4 91.744(4)8, and V 1⁄4 692.90(6) Å, whereas taniajacoite is triclinic, with space group C1 and a1⁄49.1386(5), b1⁄46.2566(3), c1⁄412.0043(6) Å, a1⁄490.019(4), b1⁄491.643(4), c 1⁄4 89.900(4)8, and V 1⁄4 686.08(6) Å. Their structures are characterized by chains of edge-sharing MnO6 octahedra extended along [010], which are linked together by corner-shared SiO4 tetrahedra in four-membered [Si4O11(OH)2] linear clusters, giving rise to a so-called ‘‘hetero-polyhedral framework’’. The large cations Sr2þ and Ca2þ occupy the seven-coordinated interstices. Unlike monoclinic ruizite and strontioruizite, taniajacoite with Sr:Ca ’ 1:1 is triclinic, owing to the ordering of Sr2þ and Ca2þ into two crystallographically distinct sites, indicating an incomplete solid solution between Ca and Sr endmembers. The unitcell volumes for ruizite, taniajacoite, and strontioruizite appear to vary linearly with the Sr/(Ca þ Sr) ratio.
{"title":"Taniajacoite and Strontioruizite, Two New Minerals Isostructural with Ruizite from the N'Chwaning III Mine, Kalahari Manganese Field, South Africa","authors":"Hexiong Yang, X. Gu, B. Cairncross, R. Downs, S. Evans","doi":"10.3749/CANMIN.2000037","DOIUrl":"https://doi.org/10.3749/CANMIN.2000037","url":null,"abstract":"Two new mineral species, taniajacoite and strontioruizite, ideally SrCaMn2Si4O11(OH)4 2H2O and Sr2Mn2 Si4O11(OH)4 2H2O, respectively, have been identified from the N’Chwaning III mine, Kalahari manganese field, South Africa. Both minerals occur as brown radiating groups or aggregates of acicular or prismatic crystals, with individual crystals up to 0.15 3 0.04 3 0.02 mm for taniajacoite and 1.3 3 0.2 3 0.2 mm for strontioruizite. Minerals associated with taniajacoite include sugilite, aegirine, pectolite, richterite, potassic-ferri-leakeite, and lipuite, whereas those associated with strontioruizite include sugilite, potassic-magnesio-arfvedsonite, and lipuite. Both taniajacoite and strontioruizite are brown in transmitted light, transparent with very light brown streak and vitreous luster. They are brittle and have a Mohs hardness of 5–5.5; cleavage is good on {010} and no parting or twinning is observed macroscopically. The measured and calculated densities are 3.05(2) and 3.09 g/cm, respectively, for taniajacoite and 3.20(2) and 3.16 g/cm for strontioruizite. Optically, both taniajacoite and strontioruizite are biaxial (–), with a1⁄4 1.686(2), b1⁄4 1.729(2), c1⁄4 1.746(2) (white light), 2V (meas.)1⁄4 63.7(5)8, 2V (calc.)1⁄4 62.58 for the former and a1⁄4 1.692(2), b1⁄4 1.734(2), c1⁄4 1.747(2) (white light), 2V (meas.)1⁄4 59.1(5)8, 2V (calc.)1⁄4 56.68 for the latter. The calculated compatibility index based on the empirical formula is 0.008 for taniajacoite and 0.015 for strontioruizite. An electron microprobe analysis yielded an empirical formula (based on 17 O apfu) of Sr(Ca0.81Sr0.19)R1.00(Mn 3þ 1.90Fe 3þ 0.15 Al0.01)R2.06Si3.96O11(OH)4 2H2O for taniajacoite and (Sr1.61Ca0.42)R2.03(Mn1.95Fe0.05)R2.00Si3.98O11(OH)4 2H2O for strontioruizite. Taniajacoite and strontioruizite are isostructural with ruizite. Strontioruizite, like ruizite, is monoclinic with space group C2 and unit-cell parameters a 1⁄4 9.1575(4), b 1⁄4 6.2857(4), c 1⁄4 12.0431(6) Å, b 1⁄4 91.744(4)8, and V 1⁄4 692.90(6) Å, whereas taniajacoite is triclinic, with space group C1 and a1⁄49.1386(5), b1⁄46.2566(3), c1⁄412.0043(6) Å, a1⁄490.019(4), b1⁄491.643(4), c 1⁄4 89.900(4)8, and V 1⁄4 686.08(6) Å. Their structures are characterized by chains of edge-sharing MnO6 octahedra extended along [010], which are linked together by corner-shared SiO4 tetrahedra in four-membered [Si4O11(OH)2] linear clusters, giving rise to a so-called ‘‘hetero-polyhedral framework’’. The large cations Sr2þ and Ca2þ occupy the seven-coordinated interstices. Unlike monoclinic ruizite and strontioruizite, taniajacoite with Sr:Ca ’ 1:1 is triclinic, owing to the ordering of Sr2þ and Ca2þ into two crystallographically distinct sites, indicating an incomplete solid solution between Ca and Sr endmembers. The unitcell volumes for ruizite, taniajacoite, and strontioruizite appear to vary linearly with the Sr/(Ca þ Sr) ratio.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43239103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Lykova, R. Rowe, G. Poirier, A. McDonald, G. Giester
A new mineral, nioboheftetjernite, ideally ScNbO4, was found in the Befanamo pegmatite, Analamanga, Madagascar. It occurs as anhedral grains and very crude elongated crystals up to 200 μm in length in an intergrowth with rossovskyite, ilmenite, rutile, thortveitite, euxenite-(Y), feldspar, and quartz. The mineral is black with dark-brown to black streak and submetallic luster. It has no cleavage and its fracture is uneven. Dcalc is 5.855 g/cm3. The Raman spectrum and reflectance data are reported. The chemical composition (wt.%) is MgO 0.06, MnO 2.49, Fe2O3 12.14, Sc2O3 11.34, TiO2 5.94, SnO2 1.45, Nb2O5 32.23, Ta2O5 29.93, WO3 3.38, total 98.96. The empirical formula calculated on the basis of 4 O apfu is (Sc0.40Fe3+0.37Ti0.15Mn2+0.08)Σ1.00(Nb0.58Ta0.33W0.03Ti0.03Sn0.02)Σ0.99O4. The simplified general formula is (Sc,Fe3+)(Nb,Ta)O4. Nioboheftetjernite is monoclinic, P2/c, a = 4.7092(3), b = 5.6531(4), c = 5.0530(4) Å, β = 90.453(3)°, and V = 134.515(17) Å3. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are: 4.722(22)(100), 3.776(22)(011), 3.628(44)(110), , 2.938(83)(111), 2.472(30)(021), and . The crystal structure, refined from single-crystal X-ray diffraction data (R1 = 0.016), is of the “wolframite” type. The mineral is named as the Nb-analogue of heftetjernite, ScTaO4.
{"title":"Nioboheftetjernite, ScNbO4, a new mineral from the Befanamo Pegmatite, Madagascar","authors":"I. Lykova, R. Rowe, G. Poirier, A. McDonald, G. Giester","doi":"10.3749/CANMIN.2000070","DOIUrl":"https://doi.org/10.3749/CANMIN.2000070","url":null,"abstract":"\u0000 A new mineral, nioboheftetjernite, ideally ScNbO4, was found in the Befanamo pegmatite, Analamanga, Madagascar. It occurs as anhedral grains and very crude elongated crystals up to 200 μm in length in an intergrowth with rossovskyite, ilmenite, rutile, thortveitite, euxenite-(Y), feldspar, and quartz. The mineral is black with dark-brown to black streak and submetallic luster. It has no cleavage and its fracture is uneven. Dcalc is 5.855 g/cm3. The Raman spectrum and reflectance data are reported. The chemical composition (wt.%) is MgO 0.06, MnO 2.49, Fe2O3 12.14, Sc2O3 11.34, TiO2 5.94, SnO2 1.45, Nb2O5 32.23, Ta2O5 29.93, WO3 3.38, total 98.96. The empirical formula calculated on the basis of 4 O apfu is (Sc0.40Fe3+0.37Ti0.15Mn2+0.08)Σ1.00(Nb0.58Ta0.33W0.03Ti0.03Sn0.02)Σ0.99O4. The simplified general formula is (Sc,Fe3+)(Nb,Ta)O4. Nioboheftetjernite is monoclinic, P2/c, a = 4.7092(3), b = 5.6531(4), c = 5.0530(4) Å, β = 90.453(3)°, and V = 134.515(17) Å3. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are: 4.722(22)(100), 3.776(22)(011), 3.628(44)(110), , 2.938(83)(111), 2.472(30)(021), and . The crystal structure, refined from single-crystal X-ray diffraction data (R1 = 0.016), is of the “wolframite” type. The mineral is named as the Nb-analogue of heftetjernite, ScTaO4.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44232644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The electronic polarizabilities of most cations, such as Na+, Ca2+, Fe2+, Fe3+, and Zr4+, show a monotonic decrease as the cation coordination increases. However, polarizabilities of the ions [5]Ti4+, [5]V5+, and [6]V5+ show strong deviations from a regular decrease. In this paper we characterize the [5]Ti and vanadyl compounds by infrared frequencies, by the short [5]Ti4+– O, [5]V4+–O, [6]V4+–O, [5]V5+–O, and [6]V5+–O bonds and the polarizabilities of [5]Ti4+, [5]V4+, [6]V4+, [5]V5+, and [6]V5+ determined from refractive index measurements. Analysis of the structures of 18 compounds containing short [5]Ti–O bonds supports the concept of the short Ti–O bond being associated with the bond valence sum (omitting Ti) around the oxygen atom O*. The short Ti–O* bond occurs to satisfy the bond valence requirement of (O2–) of ∼2.0 vu. Plotting the [5]Ti–O* distances of 18 minerals versus the bond valence sum (BVS) around O* shows an approximately linear relationship. Extrapolation to BVS = 0 yields a minimum distance of 1.65 Å. The mean value is 1.693 Å. The mean short distances in V4+ vanadyl minerals are 1.597 Å (CN = 5) and 1.590 Å (CN = 6), whereas the mean short distance in five V5+ minerals is 1.647 Å (CN = 5) and in 14 V5+ minerals is 1.644 Å (CN = 6). We compare the polarizabilities of [5]Ti and [5,6]V4+ and [5,6]V5+ ions with the polarizabilities of [4]-coordinated Ti4+ ([4]Ti4+ ) and [6]-coordinated Ti4+ ([6]Ti4+ ) and of [4]-, [5]-, and [6]-coordinated V4+ and V5+ ([n]V4+ and [n]V5+) and hypothesize that the reduced polarizability of [5]Ti4+, [5]V5+, and [6]V5+ ions is caused by the short Ti–O* and V=O bonds.
{"title":"Empirical Electronic Polarizabilities for Use in Refractive Index Measurements III. Structures with Short [5]Ti–O and Vanadyl Bonds","authors":"R. D. Shannon, R. Fischer","doi":"10.3749/CANMIN.2000046","DOIUrl":"https://doi.org/10.3749/CANMIN.2000046","url":null,"abstract":"\u0000 The electronic polarizabilities of most cations, such as Na+, Ca2+, Fe2+, Fe3+, and Zr4+, show a monotonic decrease as the cation coordination increases. However, polarizabilities of the ions [5]Ti4+, [5]V5+, and [6]V5+ show strong deviations from a regular decrease. In this paper we characterize the [5]Ti and vanadyl compounds by infrared frequencies, by the short [5]Ti4+– O, [5]V4+–O, [6]V4+–O, [5]V5+–O, and [6]V5+–O bonds and the polarizabilities of [5]Ti4+, [5]V4+, [6]V4+, [5]V5+, and [6]V5+ determined from refractive index measurements. Analysis of the structures of 18 compounds containing short [5]Ti–O bonds supports the concept of the short Ti–O bond being associated with the bond valence sum (omitting Ti) around the oxygen atom O*. The short Ti–O* bond occurs to satisfy the bond valence requirement of (O2–) of ∼2.0 vu. Plotting the [5]Ti–O* distances of 18 minerals versus the bond valence sum (BVS) around O* shows an approximately linear relationship. Extrapolation to BVS = 0 yields a minimum distance of 1.65 Å. The mean value is 1.693 Å. The mean short distances in V4+ vanadyl minerals are 1.597 Å (CN = 5) and 1.590 Å (CN = 6), whereas the mean short distance in five V5+ minerals is 1.647 Å (CN = 5) and in 14 V5+ minerals is 1.644 Å (CN = 6). We compare the polarizabilities of [5]Ti and [5,6]V4+ and [5,6]V5+ ions with the polarizabilities of [4]-coordinated Ti4+ ([4]Ti4+ ) and [6]-coordinated Ti4+ ([6]Ti4+ ) and of [4]-, [5]-, and [6]-coordinated V4+ and V5+ ([n]V4+ and [n]V5+) and hypothesize that the reduced polarizability of [5]Ti4+, [5]V5+, and [6]V5+ ions is caused by the short Ti–O* and V=O bonds.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47892792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Holtstam, L. Bindi, P. Bonazzi, H. Förster, U. Andersson
Arrheniusite-(Ce) is a new mineral (IMA 2019-086) from the Östanmossa mine, one of the Bastnäs-type deposits in the Bergslagen ore region, Sweden. It occurs in a metasomatic F-rich skarn, associated with dolomite, tremolite, talc, magnetite, calcite, pyrite, dollaseite-(Ce), parisite-(Ce), bastnäsite-(Ce), fluorbritholite-(Ce), and gadolinite-(Nd). Arrheniusite-(Ce) forms anhedral, greenish-yellow translucent grains, exceptionally up to 0.8 mm in diameter. It is optically uniaxial (–), with ω = 1.750(5), ε = 1.725(5), and non-pleochroic in thin section. The calculated density is 4.78(1) g/cm3. Arrheniusite-(Ce) is trigonal, space group R3m, with unit-cell parameters a = 10.8082(3) Å, c = 27.5196(9) Å, and V = 2784.07(14) Å3 for Z = 3. The crystal structure was refined from X-ray diffraction data to R1 = 3.85% for 2286 observed reflections [Fo > 4σ(Fo)]. The empirical formula for the fragment used for the structural study, based on EPMA data and results from the structure refinement, is: (Ca0.65As3+0.35)Σ1(Mg0.57Fe2+0.30As5+0.10Al0.03)Σ1[(Ce2.24Nd2.13La0.86Gd0.74Sm0.71Pr0.37)Σ7.05(Y2.76Dy0.26Er0.11Tb0.08Tm0.01Ho0.04Yb0.01)Σ3.27Ca4.14]Σ14.46(SiO4)3[(Si3.26B2.74)Σ6O17.31F0.69][(As5+0.65Si0.22P0.13)Σ1O4](B0.77O3)F11; the ideal formula obtained is CaMg[(Ce7Y3)Ca5](SiO4)3(Si3B3O18)(AsO4)(BO3)F11. Arrheniusite-(Ce) belongs to the vicanite group of minerals and is distinct from other isostructural members mainly by having a Mg-dominant, octahedrally coordinated site (M6); it can be considered a Mg-As analog to hundholmenite-(Y). The threefold coordinated T5 site is partly occupied by B, like in laptevite-(Ce) and vicanite-(Ce). The mineral name honors C.A. Arrhenius (1757–1824), a Swedish officer and chemist, who first discovered gadolinite-(Y) from the famous Ytterby pegmatite quarry.
{"title":"Arrheniusite-(Ce), CaMg[(Ce7Y3)Ca5](SiO4)3(Si3B3O18)(AsO4)(BO3)F11, a New Member of the Vicanite Group, from the Östanmossa Mine, Norberg, Sweden","authors":"D. Holtstam, L. Bindi, P. Bonazzi, H. Förster, U. Andersson","doi":"10.3749/CANMIN.2000045","DOIUrl":"https://doi.org/10.3749/CANMIN.2000045","url":null,"abstract":"\u0000 Arrheniusite-(Ce) is a new mineral (IMA 2019-086) from the Östanmossa mine, one of the Bastnäs-type deposits in the Bergslagen ore region, Sweden. It occurs in a metasomatic F-rich skarn, associated with dolomite, tremolite, talc, magnetite, calcite, pyrite, dollaseite-(Ce), parisite-(Ce), bastnäsite-(Ce), fluorbritholite-(Ce), and gadolinite-(Nd). Arrheniusite-(Ce) forms anhedral, greenish-yellow translucent grains, exceptionally up to 0.8 mm in diameter. It is optically uniaxial (–), with ω = 1.750(5), ε = 1.725(5), and non-pleochroic in thin section. The calculated density is 4.78(1) g/cm3. Arrheniusite-(Ce) is trigonal, space group R3m, with unit-cell parameters a = 10.8082(3) Å, c = 27.5196(9) Å, and V = 2784.07(14) Å3 for Z = 3. The crystal structure was refined from X-ray diffraction data to R1 = 3.85% for 2286 observed reflections [Fo > 4σ(Fo)]. The empirical formula for the fragment used for the structural study, based on EPMA data and results from the structure refinement, is: (Ca0.65As3+0.35)Σ1(Mg0.57Fe2+0.30As5+0.10Al0.03)Σ1[(Ce2.24Nd2.13La0.86Gd0.74Sm0.71Pr0.37)Σ7.05(Y2.76Dy0.26Er0.11Tb0.08Tm0.01Ho0.04Yb0.01)Σ3.27Ca4.14]Σ14.46(SiO4)3[(Si3.26B2.74)Σ6O17.31F0.69][(As5+0.65Si0.22P0.13)Σ1O4](B0.77O3)F11; the ideal formula obtained is CaMg[(Ce7Y3)Ca5](SiO4)3(Si3B3O18)(AsO4)(BO3)F11. Arrheniusite-(Ce) belongs to the vicanite group of minerals and is distinct from other isostructural members mainly by having a Mg-dominant, octahedrally coordinated site (M6); it can be considered a Mg-As analog to hundholmenite-(Y). The threefold coordinated T5 site is partly occupied by B, like in laptevite-(Ce) and vicanite-(Ce). The mineral name honors C.A. Arrhenius (1757–1824), a Swedish officer and chemist, who first discovered gadolinite-(Y) from the famous Ytterby pegmatite quarry.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48424806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It is commonly accepted that the calculation of the proportions of endmember constituents in garnet is dependent on the particular sequence of calculating the amounts of the endmembers, and this belief has been used to justify avoiding the use of endmembers in the definition of a mineral species. Calculating the amounts of endmember constituents to represent a specific mineral formula involves the solution of a set of simultaneous equations, and hence the idea that the solution is dependent on the order in which the amounts of endmember constituent are determined conflicts with the meaning of the term “simultaneous equations”. Here I examine the data on which these conclusions are based and show that these sequence-dependent results arise because of the use of non-stoichiometric formulae that are not electroneutral. If a garnet formula is adjusted slightly such that it exactly fits the general formula of a garnet, [8]X3[6]Y2[4]Z3O12, and is electroneutral, the simultaneous equations relating its chemical formula to a set of endmember constituents have a single unique solution. Thus, the argument that has been used to justify avoiding the use of endmembers in the definition of a mineral species is specious.
{"title":"On the Calculation of the Relative Amounts of Endmember Constituents For Garnet","authors":"F. Hawthorne","doi":"10.3749/CANMIN.2000074","DOIUrl":"https://doi.org/10.3749/CANMIN.2000074","url":null,"abstract":"\u0000 It is commonly accepted that the calculation of the proportions of endmember constituents in garnet is dependent on the particular sequence of calculating the amounts of the endmembers, and this belief has been used to justify avoiding the use of endmembers in the definition of a mineral species. Calculating the amounts of endmember constituents to represent a specific mineral formula involves the solution of a set of simultaneous equations, and hence the idea that the solution is dependent on the order in which the amounts of endmember constituent are determined conflicts with the meaning of the term “simultaneous equations”. Here I examine the data on which these conclusions are based and show that these sequence-dependent results arise because of the use of non-stoichiometric formulae that are not electroneutral. If a garnet formula is adjusted slightly such that it exactly fits the general formula of a garnet, [8]X3[6]Y2[4]Z3O12, and is electroneutral, the simultaneous equations relating its chemical formula to a set of endmember constituents have a single unique solution. Thus, the argument that has been used to justify avoiding the use of endmembers in the definition of a mineral species is specious.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47097099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Agakhanov, A. Kasatkin, S. Britvin, O. Siidra, L. Pautov, I. Pekov, V. Y. Karpenko
Cesiokenopyrochlore is a new mineral belonging to the pyrochlore group. It was discovered in a specimen of granitic pegmatite collected at Tetezantsio, Betafo region, Madagascar. The mineral forms rough equant crystals up to 0.05 mm in size intergrown with béhierite and rynersonite. Cesiokenopyrochlore is light-brown, translucent, with resinous luster. Dcalc. = 5.984 g/cm3. In reflected light it is light gray, isotropic, with strong light-brown internal reflections. The crystal structure was refined to R1 = 0.0212. The mineral is cubic, , a = 10.444(1) Å, V = 1139.5(2) Å3, and Z = 8. The strongest lines of the powder X-ray diffraction pattern [d, Å, (I, %) (hkl)] are: 6.03 (37) (111), 3.70 (9) (220), 3.15 (100) (311), 3.02 (36) (222), 2.012 (17) (511, 333), 1.848 (19) (440), 1.576 (11) (622). The chemical composition is (wt.%; electron microprobe): Cs2O 22.66, Na2O 1.74, CaO 0.64, Nb2O5 20.87, Ta2O5 21.27, WO3 30.67, H2O (calc) 0.12, total 97.97. The empirical formula of the holotype specimen calculated on the basis of (Nb+Ta+W) = 2 apfu and (O+OH) = 6 apfu and written according to the pyrochlore-supergroup nomenclature is Na0.29Ca0.06(Nb0.81W0.69Ta0.50)Σ2[O5.93(OH)0.07]Σ6Cs0.83. The simplified formula of the holotype specimen is □2(Nb,W,Ta)Σ2O6Cs. Cesiokenopyrochlore is the first natural niobate to adopt the inverse pyrochlore structure.
{"title":"Cesiokenopyrochlore, the First Natural Niobate with an Inverse Pyrochlore Structure","authors":"A. Agakhanov, A. Kasatkin, S. Britvin, O. Siidra, L. Pautov, I. Pekov, V. Y. Karpenko","doi":"10.3749/CANMIN.2000056","DOIUrl":"https://doi.org/10.3749/CANMIN.2000056","url":null,"abstract":"\u0000 Cesiokenopyrochlore is a new mineral belonging to the pyrochlore group. It was discovered in a specimen of granitic pegmatite collected at Tetezantsio, Betafo region, Madagascar. The mineral forms rough equant crystals up to 0.05 mm in size intergrown with béhierite and rynersonite. Cesiokenopyrochlore is light-brown, translucent, with resinous luster. Dcalc. = 5.984 g/cm3. In reflected light it is light gray, isotropic, with strong light-brown internal reflections. The crystal structure was refined to R1 = 0.0212. The mineral is cubic, , a = 10.444(1) Å, V = 1139.5(2) Å3, and Z = 8. The strongest lines of the powder X-ray diffraction pattern [d, Å, (I, %) (hkl)] are: 6.03 (37) (111), 3.70 (9) (220), 3.15 (100) (311), 3.02 (36) (222), 2.012 (17) (511, 333), 1.848 (19) (440), 1.576 (11) (622). The chemical composition is (wt.%; electron microprobe): Cs2O 22.66, Na2O 1.74, CaO 0.64, Nb2O5 20.87, Ta2O5 21.27, WO3 30.67, H2O (calc) 0.12, total 97.97. The empirical formula of the holotype specimen calculated on the basis of (Nb+Ta+W) = 2 apfu and (O+OH) = 6 apfu and written according to the pyrochlore-supergroup nomenclature is Na0.29Ca0.06(Nb0.81W0.69Ta0.50)Σ2[O5.93(OH)0.07]Σ6Cs0.83. The simplified formula of the holotype specimen is □2(Nb,W,Ta)Σ2O6Cs. Cesiokenopyrochlore is the first natural niobate to adopt the inverse pyrochlore structure.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48600536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Garate-Olave, E. Roda-Robles, P. Gil-Crespo, A. Pesquera
In the Tres Arroyos granite-pegmatite system (Badajoz, Spain) a zoned aplite-pegmatite field occurs, with poorly evolved, intermediate, and Li-rich dikes intruded into metasediments, close to the contact with the Nisa-Alburquerque granitic batholith. A large variety of Fe-Mn phosphate minerals occur in the poorly evolved aplite-pegmatites; Al-phosphates occur mainly in the intermediate and Li-rich dikes. The Fe/(Fe + Mn) ratio of the Fe-Mn phosphates is the highest reported for aplite-pegmatite fields in the Central Iberian Zone, suggesting a low degree of fractionation for the poorly evolved aplite-pegmatites that host these minerals. In contrast, the high F contents observed in crystals of the amblygonite–montebrasite series from the intermediate and Li-rich aplite-pegmatites indicates a higher fractionation degree for these dikes. The relatively common occurrence of phosphate minerals in the three types of aplite-pegmatites from Tres Arroyos attests to a significant availability of P in the pegmatitic melt. In this granite pegmatite system, P first started behaving as a compatible element, thus favoring the crystallization of discrete phosphates, during the crystallization of the poorly evolved aplite-pegmatites. In more fractionated melts, where Fe-Mn-(Mg) contents were extremely depleted, P was still available, allowing the crystallization of the Al-phosphates, mainly of the amblygonite–montebrasite series, in the more evolved intermediate and Li-rich aplite-pegmatites. Subsolidus replacement of the early phosphate phases, such as those of the amblygonite–montebrasite series, by lacroixite, together with the presence of late Ca- and Sr-bearing phosphates such as jahnsite-(CaMnFe), whiteite-(CaFeMg), mitridatite, and goyazite, attest to a high activity of metasomatic fluids in the Tres Arroyos granite-pegmatite system. Consequently, variations in the phosphate mineral associations and in their chemical compositions reflect well the fractional crystallization processes suffered by the pegmatitic melts from the poorly evolved up to the Li-rich dikes, as well as the subsolidus history of the Tres Arroyos system.
{"title":"Phosphate mineral associations from the Tres Arroyos aplite-pegmatites (Badajoz, Spain): Petrography, mineral chemistry, and petrogenetic implications","authors":"I. Garate-Olave, E. Roda-Robles, P. Gil-Crespo, A. Pesquera","doi":"10.3749/CANMIN.1900102","DOIUrl":"https://doi.org/10.3749/CANMIN.1900102","url":null,"abstract":"In the Tres Arroyos granite-pegmatite system (Badajoz, Spain) a zoned aplite-pegmatite field occurs, with poorly evolved, intermediate, and Li-rich dikes intruded into metasediments, close to the contact with the Nisa-Alburquerque granitic batholith. A large variety of Fe-Mn phosphate minerals occur in the poorly evolved aplite-pegmatites; Al-phosphates occur mainly in the intermediate and Li-rich dikes. The Fe/(Fe + Mn) ratio of the Fe-Mn phosphates is the highest reported for aplite-pegmatite fields in the Central Iberian Zone, suggesting a low degree of fractionation for the poorly evolved aplite-pegmatites that host these minerals. In contrast, the high F contents observed in crystals of the amblygonite–montebrasite series from the intermediate and Li-rich aplite-pegmatites indicates a higher fractionation degree for these dikes. The relatively common occurrence of phosphate minerals in the three types of aplite-pegmatites from Tres Arroyos attests to a significant availability of P in the pegmatitic melt. In this granite pegmatite system, P first started behaving as a compatible element, thus favoring the crystallization of discrete phosphates, during the crystallization of the poorly evolved aplite-pegmatites. In more fractionated melts, where Fe-Mn-(Mg) contents were extremely depleted, P was still available, allowing the crystallization of the Al-phosphates, mainly of the amblygonite–montebrasite series, in the more evolved intermediate and Li-rich aplite-pegmatites. Subsolidus replacement of the early phosphate phases, such as those of the amblygonite–montebrasite series, by lacroixite, together with the presence of late Ca- and Sr-bearing phosphates such as jahnsite-(CaMnFe), whiteite-(CaFeMg), mitridatite, and goyazite, attest to a high activity of metasomatic fluids in the Tres Arroyos granite-pegmatite system. Consequently, variations in the phosphate mineral associations and in their chemical compositions reflect well the fractional crystallization processes suffered by the pegmatitic melts from the poorly evolved up to the Li-rich dikes, as well as the subsolidus history of the Tres Arroyos system.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42762235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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