The Canadian Journal of Mineralogy and Petrology最新文献

{"title":"Two Rinkite-Group (Seidozerite-Supergroup) Minerals: Nacareniobsite-(Y), a New Mineral from the Darai-Pioz Alkaline Massif, Tajikistan, and Crystal-Structure Refinement of Nacareniobsite-(Ce)","authors":"Atali A. Agakhanov, Maxwell C. Day, Elena Sokolova, Vladimir Yu. Karpenko, Frank C. Hawthorne, Leonid A. Pautov, Igor V. Pekov, Anatoly V. Kasatkin, Vitalia A. Agakhanova","doi":"10.3749/2300029","DOIUrl":"https://doi.org/10.3749/2300029","url":null,"abstract":"Abstract Nacareniobsite-(Y), ideally Na3Ca3YNb(Si2O7)2OF3, is a new rinkite-group (seidozerite-supergroup) TS-block mineral from the Darai-Pioz alkaline massif, Tien-Shan mountains, Tajikistan. The mineral is of hydrothermal origin. It occurs as prismatic crystals up to 1 mm long and 0.1 mm thick embedded in an aggregate of coarse-grained reedmergnerite. Associated minerals are reedmergnerite, leucophanite, nordite-(Ce), microcline, zeravshanite, polylithionite, kentbrooksite, yusupovite, fluornatropyrochlore, and quartz. Crystals are pale yellow, transparent, with a vitreous to translucent luster. Nacareniobsite-(Y) has a white streak, uneven to conchoidal fracture, and does not fluoresce under cathode or ultraviolet light. Cleavage is {100} very good, no parting was observed, Mohs hardness is 5, and it is brittle, Dmeas. = 3.49(2) g/cm3, Dcalc. = 3.515 g/cm3. It is biaxial (+) with refractive indices (λ = 590 nm) α = 1.662(2), β = 1.668(2), γ = 1.690(2); 2Vcalc. = 56°. It is nonpleochroic. Nacareniobsite-(Y) is monoclinic, space group P21/c, a = 7.4069(15), b = 5.6540(11), c = 18.787(4) Å, β = 101.36(3)°, V = 771.3(3) Å3. The six strongest reflections in the X-ray powder diffraction data [d(Å), I, (h k l)] are: 3.068, 100, (0 0 6, 1 2, 2 1 0); 2.944, 45, (2 1 1, 1 3); 2.707, 32, (0 2 2, 0 1 6); 5.44, 31, (0 1 1); 1.853, 29, ( 0 2, 2 1 7, 1 9); 3.59, 26, (1 0 4, 0 1 4). The empirical formula calculated on the basis of 18 (O + F) is Na2.82Ca3.06Sr0.14[Y0.37(Nd0.16Ce0.15Dy0.08Gd0.06Sm0.05La0.04Tb0.02Ho0.02Lu0.02Pr0.01Eu0.01Tm0.01Er0.01Yb0.01)Σ0.65]Σ1.02(Nb0.63Ti0.38)Σ1.01(Si4.00O14)O1.00F3.00, Z = 2. The ideal formula is Na3Ca3YNb(Si2O7)2OF3. The crystal structure was refined on a twinned crystal to R1 = 3.50% on the basis of 1788 unique reflections (Fo > 4σFo). It is a framework of TS (Titanium-Silicate) blocks where the TS block consists of HOH sheets (H = heteropolyhedral, O = octahedral) parallel to (100). In the O sheet, the Nb-dominant [6]MO(1) site is ideally occupied by one Nb apfu. The [8]MO(2) and [6]MO(3) sites are ideally occupied by one Na and two Na apfu, respectively. The H sheet contains two unique sites: the [7]MH site, ideally (CaY), is occupied by Ca1.23(Y0.37Ln0.40)Σ0.77, with <MH–φ> = 2.424 Å, and the [7]AP site, ideally Ca2, is occupied by Ca1.61Sr0.14Ln0.25, with <AP–φ> = 2.469 Å. The AP+ MH sites ideally give Ca2(CaY) apfu. The MH and AP polyhedra and Si2O7 groups constitute the H sheet. Linkages of the H and O sheets via common vertices of the MH and AP polyhedra, and Si2O7 groups with MO(1–3) polyhedra, results in the TS block. The TS block in nacareniobsite-(Y) exhibits linkage 1 and has a stereochemistry typical for the rinkite group (Ti + Nb + Zr = 1 apfu) of the seidozerite supergroup. For nacareniobsite-(Y), the ideal structural formula of the form AP2MH2MO4(Si2O7)2(XOM)2(XOA)2 is Ca2(CaY)Na3Nb(Si2O7)2(OF)F2. The mineral is named nacareniobsite-(Y), as it is structurally identical t","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135111739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sidorovite, PtFe3, A New Mineral from the Snegovaya River Placer, Koryak Highlands, Russia","authors":"Anton Kutyrev, Andrew M. Mcdonald, Nobumichi Tamura, L. Cabri, Nadezhda Tolstykh, I. Pekov","doi":"10.3749/2200072","DOIUrl":"https://doi.org/10.3749/2200072","url":null,"abstract":"\u0000 Sidorovite, ideally PtFe3, is a new mineral from the Epilchik ultramafic complex and nearby Snegovaya River placer, Koryak Highlands, Russia. It was found in isoferroplatinum grains extracted from a heavy-mineral concentrate obtained from crushed lode chromitites and alluvial material. Sidorovite occurs either as a part of complex grains comprising tetraferroplatinum, native iron, hollingworthite, magnetite, serpentine, and chromite or as part of secondary rims which formed together with tetraferroplatinum after isoferroplatinum. According to the Laue pattern obtained by synchrotron microdiffraction, sidorovite is cubic, crystallizing in space group Pm3¯m and adopting an Au3Cu-type crystal structure. Its unit-cell parameters are a = 3.725(4) Å, V = 51.687(4) Å3, Z = 1. The calculated density is 11.815 g/cm3. The strongest X-ray diffraction lines are [d (Å) (I, %) (hkl)] 2.161 (100) (111), 3.711 (48) (100), 1.871 (36) (200), 1.673 (27) (210). No cleavage was observed and hardness could not be determined owing to the small size of the grains. The empirical formula of sidorovite calculated based on four atoms is: Pt1.04(Fe2.89Cu0.05Ni0.02)Σ2.96. The mineral is posited to form through the incorporation of Fe0 by tetraferroplatinum, which arises through the reduction of Fe via H2-bearing fluids produced through the serpentinization of olivine at T < 450 °C. The name of the new mineral honors the Russian geologist and mineralogist Evgeniy Gennadievich Sidorov (1955–2021).","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"212 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132664244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shinkolobweite, from the Shinkolobwe Mine, Democratic Republic of Congo: A New Mineral Containing Uranium in the Rare Pentavalent Oxidation State","authors":"Travis A. Olds, Aaron J. Lussier, Václav PetŘíček, Jakub Plášil, Anthony R. Kampf, Allen G. Oliver, Peter C. Burns, Mateusz Dembowski, Ian M. Steele","doi":"10.3749/2300003","DOIUrl":"https://doi.org/10.3749/2300003","url":null,"abstract":"ABSTRACT Shinkolobweite, Pb1.333[U5+O(OH)(UO2)5O4.67(OH)5.33](H2O)5, is a new lead uranyl oxide-hydroxide hydrate mineral containing hexavalent and pentavalent uranium from the Shinkolobwe mine, Democratic Republic of Congo. Crystals of shinkolobweite are dark reddish-brown prisms up to 0.5 mm in length, occurring on a matrix of massive uraninite associated with fourmarierite, rutherfordine, soddyite, and sklodowskite. Crystals are translucent with subadamantine luster and light bronze-yellow streak, are flattened on {010}, are elongated on [001], and exhibit the forms {100}, {010}, {101}, and . The mineral is non-fluorescent under both longwave and shortwave ultraviolet illumination. It has a Mohs hardness of ∼2 and exhibits brittle tenacity with perfect cleavage on {010}, imperfect cleavage on {100}, and even fracture. The calculated density is 5.853 g/cm3 based on the empirical formula. Electron probe microanalysis provided the empirical formula Pb1.290U6+4.876U5+1.166O27H16.633 based on 27 O apfu and U5+:U6+ determined by X-ray photoelectron spectroscopy. Shinkolobweite is orthorhombic, superspace group Pnnm(0b0)000, a = 14.4808(4), b = 7.0681(8), c = 11.9423(3) Å, V = 1222.32(15) Å3, modulation wave vector [0 1/3 0], and Z = 2. The structure was refined from 8959 reflections to a final R1 = 0.0736 for all reflections. Uranyl oxide-hydroxide sheets in shinkolobweite adopt the β-U3O8 topology and possess (3 + 1) commensurately modulated ordering that results from the long-range ordering of U5+ and U6+ in the sheet, as well as the position and occupancy of interlayer Pb2+ cations. Observations of a topological transition between α-U3O8 and β-U3O8 type sheets in shinkolobweite supplements our understanding of U5+ mineral oxidation and stability.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135588377","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Discreditation of <i>Platarsite</i>: A S-Rich Variety of Sperrylite","authors":"Andrew M. Mcdonald, Louis J. Cabri","doi":"10.3749/2300021","DOIUrl":"https://doi.org/10.3749/2300021","url":null,"abstract":"Abstract Platarsite is a relatively uncommon platinum-group mineral, reported from several world-wide localities, that has been defined as both Pt(As,S)2 and PtAsS in the literature. It was first described using material from the Onverwacht mine, eastern Bushveld Complex, Republic of South Africa, where it occurs with genkinite, geversite, and Pt-Fe alloy. Data from chemical analyses indicate (1) Pt is the dominant PGE, but with significant enrichments of both Rh and Ru; (2) ΣAs+S ∼ 2; (3) ΣPGE:ΣAs+S ∼ 1:2; and (4) As:S ratios of ∼1 (but with most data showing As &amp;gt; S), all of which suggest either PtAsS or Pt(As,S)2 as ideal compositions. Results from crystal-structure analyses conducted on both platarsite and sperrylite (Szymański 1979) demonstrate that the two are isostructural, both crystallizing in the cubic space group Pa3, with refined unit-cell edges of 5.788(1) and 5.9681(1) Å, respectively. They possess a pyrite-like crystal structure that includes a single metal site and a single anion site. The latter indicates that As and S, even if present in ratios of ∼1, must be disordered over a single site, rather than occupying two separate crystallographic sites. A re-evaluation of the available chemical data, along with the results from crystal-structure analyses, indicate that platarsite is a S-enriched variety of sperrylite and, as such, it has been discredited as a valid mineral species.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135299094","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Genesis and New Mineral Chemistry Data of Carlosbarbosaite, a Potential U and Nb Ore Source from Miarolitic-, A-Type Granites and NYF Pegmatites of the La Chinchilla Pluton, Velasco Ranges, La Rioja, Argentina","authors":"Raúl Lira, Francisco J. Parra, Marco E. Biglia, Orquídea Morello, Alina B. Guereschi","doi":"10.3749/2300008","DOIUrl":"https://doi.org/10.3749/2300008","url":null,"abstract":"Abstract The La Chinchilla granite is a ∼3.75 km2 epizonal pluton of Lower Carboniferous age located in Sierra de Velasco, Sierras Pampeanas, Argentina. Equigranular micropegmatitic and porphyritic main granite types host abundant millimeter- to &amp;lt;2 m-sized miarolitic pegmatites and pockets of simple major mineralogy (±beryl). Both granite types host micrometer-sized accessory species [i.e., monazite-(Ce), several high field strength element oxide species, ilmenite, cassiterite, fluorapatite] and fluorite. A F-Na-rich fluid phase promoted strong albitization at late-miarolitic stages, along with crystallization of extremely F-rich polylithionite and fluorite, and the formation of replacing pyrochlore group species associated with a second generation of cassiterite. The increase of the Ta# from hydroxycalciopyrochlore to hydroxycalciomicrolite and from micromiarolitic cassiterite (cassiterite 1) to hydrothermal cassiterite (cassiterite 2) supports Nb-Ta fractionation at hydrothermal temperatures. Carlosbarbosaite [(UO2)2Nb2O6(OH)2·2H2O] occurs as a pseudomorphic or short-range transported phase. Low-T, hydrothermal carlosbarbosaite formed after the replacement of columbite-(Fe), U-free Nb-bearing ilmenite, and likely after U-bearing pyrochlore supergroup species and a columbite group mineral, plausibly due to interaction with a hydrothermal, U6+(±Nb±Ta)-enriched fluid, in some cases a SiO2-bearing fluid. This fluid likely represents a lower T, less alkaline, and more oxidizing fluid that evolved from the higher T F-Na-rich fluids active during the late-miarolitic hydrothermal stage. Low-T, hydrothermal carlosbarbosaite has the ideal U-,Nb-rich endmember composition, though it is significantly richer in Ca and poorer in total Nb+Ta but with higher Nb# than that from the type locality. Supergene fluids deposited the transported type, which attained economic concentrations in a fault zone where restricted, likely alkaline oxidizing conditions could have favored Nb mobility.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135297911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stibiotantalite from the Nanyangshan LCT Pegmatite, North Qinling Orogen, Central China: Occurrence and New Data on its Crystal Chemistry","authors":"Kai Qu, Pei Ni, Guang Fan, Guowu Li, Yanjuan Wang","doi":"10.3749/2300018","DOIUrl":"https://doi.org/10.3749/2300018","url":null,"abstract":"\u0000 Stibiotantalite, SbTaO4, from the Nanyangshan LCT pegmatite, North Qinling Orogen, Central China is described. The mineral is associated with oxystibiomicrolite, oxycalcioroméite, hydrokenomicrolite, hydroxynatromicrolite, hydromicrolite, stibnite, bismuthinite, tantalite-(Mn), columbite-(Mn), spodumene, polylithionite, trilithionite, luanshiweiite, fluorluanshiweiite, elbaite, albite, and quartz. Results from electron microprobe data analysis (n = 4) yield the average empirical formula (based on O = 4): (Sb0.96Bi0.04)Σ1.00(Ta0.85Nb0.15)Σ1.00O4. The seven strongest X-ray powder diffraction lines are [d in Å (I)(hkl)] 3.126(100)(121), 2.964(81)(040), 5.976(27)(020), 3.515(22)(111), 1.891(22)(240), 1.736(19)(161), and 2.693(16)(131). Single-crystal X-ray diffraction (SXRD) patterns show strong reflections consistent with space group Pna21. The refined unit-cell parameters from the SXRD data are a 5.5419(2) Å, b 4.9200(2) Å, c 11.8003(5) Å, and V 321.75(2) Å3 with Z = 4. The structure has been refined to a final R1 = 0.0173 on the basis of 766 reflections with Fo > 4σ(Fo). In the previous study, the AO6 octahedron of stibiotantalite was close to an ideal octahedron. The new structure refinement of stibiotantalite from the Nanyangshan pegmatite indicates that the AO6 octahedron has a larger distortion due to the lone-pair effect of Sb3+. The high-quality structural data presented in this study gives a more accurate portrayal of the crystal structure of stibiotantalite than provided in the original description of the mineral.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117235031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Use of Pyrite Chemistry to Vector toward Gold Mineralization, an Example from the Drogo Prospect, Nunavut, Canada","authors":"Nicole Freij, D. Gregory, Rémi Verschelden, O. Côté-Mantha","doi":"10.3749/2200071","DOIUrl":"https://doi.org/10.3749/2200071","url":null,"abstract":"\u0000 Anomalous high grade Au mineralization has been found in float material at the Drogo Prospect, Nunavut, Canada. However, traditional exploration methods have thus far been unable to find the bedrock source of the mineralization. Recent studies have shown that pyrite trace element chemistry, as determined using LA-ICP-MS, varies between Au-forming and barren fluids. To test whether this also occurred at the Drogo Prospect, we analyzed pyrite in rock samples, including Au-rich samples, moderate Au grade samples, and barren samples. However, little variation in pyrite trace element chemistry was observed, suggesting that pyrite trace element chemistry may not be an effective exploration tool at the Drogo Prospect. To confirm these observations, cluster analysis was used to determine if natural clustering of the data could highlight which samples were more likely to be Au rich; again, no statistical differences could be found between the samples. In contrast to our working hypothesis, this suggests that pyrite trace element chemistry is not an effective exploration tool to find the bedrock source of the Drogo boulder trend.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"2 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126029849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Atomic Arrangement of the Sherwoodite Structural Unit: Redefinition of the Sherwoodite Vanadoaluminate Heteropoly Complex as [AlV4+V5+12O39]11−","authors":"John M. Hughes, A. R. Kampf, B. Nash, J. Marty","doi":"10.3749/2300002","DOIUrl":"https://doi.org/10.3749/2300002","url":null,"abstract":"\u0000 Sherwoodite, putatively Ca4.5(AlV5+12V4+2O40)·28H2O, was among the early naturally occurring polyoxometalates to be reported from the Uravan Mineral Belt; the ideal formula of sherwoodite is here redefined as Ca5.5[AlV4+V5+12O39]·28H2O. In an earlier preliminary structure report (R = 22%), researchers defined the composition of vanadoaluminate heteropoly complex in sherwoodite as (AlV4+,5+14O40)n−, the first natural occurrence of that polyoxometalate cluster. The cluster forms a framework around intermolecular channels that contain disordered arrays of H2O and charge-balancing Ca ions. A detailed structure study described herein [a = 27.9085(7), c = 13.8090(5), space group I41/amd, R1 < 6%] reveals new details of the vanadoaluminate heteropoly complex, indicating that it crystallizes as a structural variant of the putative (AlV4+,5+14O40)n− vanadoaluminate complex, [AlV4+V5+12O39]11−. That variant is derived through the random removal of one of the two apical vanadate octahedra, elucidating the cause of difficulties in the refinement of the preliminary structure report. The [AlV4+V5+12O39]11− complex is capped on one end by a Ca atom that bonds to four octahedral apices in a half-occupied site, and on the opposite end by the V1 and O1 atoms in half-occupied sites, similar to the compound potassium 13-vanadanomangate(IV). The capping octahedron is the locus of the V4+ ions in the mixed-valence complex. New electron microprobe analyses yielded an empirical formula, on the basis of (V4+V5+12), of (Ca4.26Mg1.09Na0.35K0.04Sr0.03)[Al0.87(V4+V5+12)O39]·28.15 H2O.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115202356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petermegawite, Al6(Se4+O3)3[SiO3(OH)](OH)9⋅10H2O, a New AI-Bearing Selenite Mineral, from the El Dragón Mine, Potosí, Bolivia","authors":"Hexiong Yang, X. Gu, Michael M. Scott, R. Jenkins, R. Gibbs, J. McGlasson, R. Downs","doi":"10.3749/2300004","DOIUrl":"https://doi.org/10.3749/2300004","url":null,"abstract":"\u0000 A new mineral species, petermegawite, ideally Al6(Se4+O3)3[SiO3(OH)](OH)9⋅10H2O, was discovered at the El Dragón mine, Potosí Department, Bolivia. It occurs as aggregates of bladed or tabular crystals. Associated minerals are Co-bearing krut′aite–penroseite (matrix), chalcomenite, ‘clinochalcomenite’ (not IMA approved), molybdomenite, lepidocrocite, goethite, ahlfeldite, and calcite. Petermegawite is colorless in transmitted light and transparent with a white streak and vitreous luster. It is brittle and has a Mohs hardness of 2–2½. Cleavage is perfect on {001}. The measured and calculated densities are 2.27(5) and 2.32 g/cm3, respectively. Optically, petermegawite is biaxial (+), with α = 1.545(5), β = 1.554(5), γ = 1.567(5) (white light). An electron microprobe analysis yielded an empirical formula (based on 10 non-H cations pfu) of Al6.00[(Se0.89S0.11)Σ1.00O3]3[(Si0.90Al0.07)Σ0.97O2.81(OH)1.19](OH)9⋅10H2O, which can be simplified to Al6[(Se,S)O3]3[(Si,Al)O3(OH)](OH)9⋅10H2O.\u0000 Petermegawite is orthorhombic, space group Cmc21 with unit-cell parameters a = 16.2392(2), b = 10.96370(10), c = 15.3367(2) Å, V = 2730.57(5) Å3, and Z = 4. Its crystal structure is characterized by clusters of six-membered rings of edge-sharing AlO6 octahedra with an SiO3(OH) tetrahedron situated at the center of each ring and three Se4+O3 triangular pyramids appended outside the ring. These clusters are joined together by hydrogen bonds to form heteropolyhedral layers parallel to (001). The H2O molecules that are not bonded to any non-H cations are sandwiched between the layers. The cluster formed by a six-membered AlO6 octahedral ring with an SiO3OH tetrahedron at the center of the ring in petermegawite has the composition [Al6(SiO3OH)O6(OH)9(H2O)6]6−. It is topologically identical to the clusters of composition [Al6(AsO4)O7(OH)9(H2O)5]8− that are found in bettertonite and penberthycroftite. As a new polyoxometalate building block, this type of cluster may be expressed with a general chemical formula [TM6X25], where T = tetrahedrally coordinated cation, M = octahedrally coordinated cation, and X = O, OH, H2O.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"162 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122864784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Picture-Perfect Petrography: Affordable Thin-Section Scanning for Geoscientists in the Digital Era","authors":"Derek. D. V. Leung, A. McDonald","doi":"10.3749/2300038","DOIUrl":"https://doi.org/10.3749/2300038","url":null,"abstract":"","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133146678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}