The wallpaper-type crystal structure of wightmanite, Mg5(BO3)O(OH)5·1–2H2O, has been reanalyzed in order to better understand the position and bonding of hydrogen atoms. Single-crystal structure refinement yielded the monoclinic I2/m unit cell a = 13.5165(18), b = 3.0981(3), c = 18.170(3)Å, ß = 91.441(6)°, and V = 760.65(17)Å3, Z = 4. Hydrogen atoms of OH groups pointing to the inside of the elliptical channels oriented parallel to [010] are arranged in the form of two overlying, a–c parallel planar pentagons. The two pentagons point in opposite directions. Hydrogen-bond analysis shows that the hydroxyl groups are linked by complex polyfurcated, intra-molecular hydrogen bonds forming a web-like network coating the walls of the channels. The longest distance between hydrogens (7.226 Å) is observed in the pentagonal planes of the channel. The anisotropically refined oxygen atoms of the zeolitic water show their strongest vibration parallel to the b axis and in the direction of the largest diameter of the elliptical channel and similarly form a complex inter-molecular hydrogen-bond system to the hydroxyl groups coating the channel walls. This complex bonding is expressed in the Raman spectrum by a broad band between 3100 and 3300 cm–1 that is assigned to the OH / H2O stretching mode and one strong band at 3661 cm–1 attributable to an OH-stretching mode. Infrared spectra also show a pronounced broad band between 3200 and 3700 cm–1 attributed to H2O and OH-stretching modes. The weak bands around 1600 cm–1 observed in the Raman and IR spectra are probably due to relatively weakly bound water in the channels.
{"title":"Complex Weblike Hydrogen Bonding in Large “Drain Pipe” Channels of Wightmanite Revealed by New X-Ray and Spectroscopic Measurements","authors":"B. W. Liebich, A. Kampf, E. Gnos, C. Schnyder","doi":"10.3749/CANMIN.2000084","DOIUrl":"https://doi.org/10.3749/CANMIN.2000084","url":null,"abstract":"\u0000 The wallpaper-type crystal structure of wightmanite, Mg5(BO3)O(OH)5·1–2H2O, has been reanalyzed in order to better understand the position and bonding of hydrogen atoms. Single-crystal structure refinement yielded the monoclinic I2/m unit cell a = 13.5165(18), b = 3.0981(3), c = 18.170(3)Å, ß = 91.441(6)°, and V = 760.65(17)Å3, Z = 4. Hydrogen atoms of OH groups pointing to the inside of the elliptical channels oriented parallel to [010] are arranged in the form of two overlying, a–c parallel planar pentagons. The two pentagons point in opposite directions. Hydrogen-bond analysis shows that the hydroxyl groups are linked by complex polyfurcated, intra-molecular hydrogen bonds forming a web-like network coating the walls of the channels. The longest distance between hydrogens (7.226 Å) is observed in the pentagonal planes of the channel. The anisotropically refined oxygen atoms of the zeolitic water show their strongest vibration parallel to the b axis and in the direction of the largest diameter of the elliptical channel and similarly form a complex inter-molecular hydrogen-bond system to the hydroxyl groups coating the channel walls. This complex bonding is expressed in the Raman spectrum by a broad band between 3100 and 3300 cm–1 that is assigned to the OH / H2O stretching mode and one strong band at 3661 cm–1 attributable to an OH-stretching mode. Infrared spectra also show a pronounced broad band between 3200 and 3700 cm–1 attributed to H2O and OH-stretching modes. The weak bands around 1600 cm–1 observed in the Raman and IR spectra are probably due to relatively weakly bound water in the channels.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41495366","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}
E. Sokolova, Maxwell C. Day, F. Hawthorne, A. Agakhanov, F. Cámara, Y. Uvarova, G. Ventura
The crystal structure of perraultite from the Oktyabr'skii massif, Donetsk region, Ukraine (bafertisite group, seidozerite supergroup), ideally NaBaMn4Ti2(Si2O7)2O2(OH)2F, Z = 4, was refined in space group C to R1 = 2.08% on the basis of 4839 unique reflections [Fo > 4σFo]; a = 10.741(6), b = 13.841(8), c = 11.079(6) Å, α = 108.174(6), β = 99.186(6), γ = 89.99(1)°, V = 1542.7(2.7) Å3. Refinement was done using data from a crystal with three twin domains which was part of a grain used for electron probe microanalysis. In the perraultite structure [structure type B1(BG), B – basic, BG – bafertisite group], there is one type of TS (Titanium-Silicate) block and one type of I (Intermediate) block; they alternate along c. The TS block consists of HOH sheets (H – heteropolyhedral, O – octahedral). In the O sheet, the ideal composition of the five [6]MO sites is Mn4apfu. There is no order of Mn and Fe2+ in the O sheet. The MH octahedra and Si2O7 groups constitute the H sheet. The ideal composition of the two [6]MH sites is Ti2apfu. The TS blocks link via common vertices of MH octahedra. The I block contains AP(1,2) and BP(1,2) cation sites. The AP(1) site is occupied by Ba and the AP(2) site by K > Ba; the ideal composition of the AP(1,2) sites is Ba apfu. The BP(1) and BP(2) sites are each occupied by Na > Ca; the ideal composition of the BP(1,2) sites is Na apfu. We compare perraultite and surkhobite based on the work of Sokolova et al. (2020) on the holotype sample of surkhobite: space group C, R1 = 2.85 %, a = 10.728(6), b = 13.845(8), c = 11.072(6) Å, α = 108.185(6), β = 99.219(5), γ = 90.001(8)°, V = 1540.0(2.5) Å3; new EPMA data. We show that (1) perraultite and surkhobite have identical chemical composition and ideal formula NaBaMn4Ti2(Si2O7)2O2(OH)2F; (2) perraultite and surkhobite are isostructural, with no order of Na and Ca at the BP(1,2) sites. Perraultite was described in 1991 and has precedence over surkhobite, which was redefined as “a Ca-ordered analogue of perraultite” in 2008. Surkhobite is not a valid mineral species and its discreditation was approved by CNMNC IMA (IMA 20-A).
乌克兰顿涅茨克地区Oktyabr'skii地块(钡长石群，钡长石超群)的透武长石晶体结构，理想为NaBaMn4Ti2(Si2O7)2O2(OH)2F, Z = 4，在空间群C中根据4839次独特反射[Fo > 4σFo]，将其细化为R1 = 2.08%;= 10.741 (6), b = 13.841 (8), c = 11.079(6),α= 108.174(6),β= 99.186(6),γ= 89.99(1)°,V = 1542.7 (2.7) A3。细化是使用数据从晶体的三个双畴，这是用于电子探针微分析晶粒的一部分。在透武质构造[构造类型B1(BG)、B -基性、BG -杂灰岩群]中，存在TS(硅酸钛)型块体和I(中间)型块体各1种;TS区由HOH片(H -异多面体，O -八面体)组成。在O层中，5个[6]MO位的理想组成是Mn4apfu。O片中Mn和Fe2+没有顺序。MH八面体和Si2O7基团构成H层。两个b[6]MH位点的理想组合是Ti2apfu。TS块通过MH八面体的公共顶点连接。I区包含AP(1,2)和BP(1,2)阳离子位点。AP(1)位点被Ba占据，AP(2)位点被k> Ba占据;AP(1,2)位点的理想组合是Ba apfu。BP(1)和BP(2)位点均由Na > Ca占据;BP(1,2)位点的理想组成是Na apfu。根据Sokolova et al.(2020)的研究成果，我们比较了透玄石与顺石:空间群C, R1 = 2.85%， a = 10.728(6)， b = 13.845(8)， C = 11.072(6) Å， α = 108.185(6)， β = 99.219(5)， γ = 90.001(8)°，V = 1540.0(2.5) Å3;新的EPMA数据。结果表明:(1)过孔石与顺石英具有相同的化学成分和理想配方NaBaMn4Ti2(Si2O7)2O2(OH)2F;(2)在BP(1,2)的位置上，过玄武岩和顺面岩体是等构造的，没有Na和Ca的顺序。peraulite于1991年被描述，优先于顺滑石，后者在2008年被重新定义为“钙阶peraulite的类似物”。surkhobit不是一种有效的矿物，已通过CNMNC IMA (IMA 20-A)的认定。
{"title":"From Structure Topology to Chemical Composition. XXIX. Revision of the Crystal Structure of Perraultite, NaBaMn4Ti2(Si2O7)2O2(OH)2F, a Seidozerite-Supergroup TS-Block Mineral from the Oktyabr'skii Massif, Ukraine, and Discreditation of Surkhobite","authors":"E. Sokolova, Maxwell C. Day, F. Hawthorne, A. Agakhanov, F. Cámara, Y. Uvarova, G. Ventura","doi":"10.3749/CANMIN.2000066","DOIUrl":"https://doi.org/10.3749/CANMIN.2000066","url":null,"abstract":"\u0000 The crystal structure of perraultite from the Oktyabr'skii massif, Donetsk region, Ukraine (bafertisite group, seidozerite supergroup), ideally NaBaMn4Ti2(Si2O7)2O2(OH)2F, Z = 4, was refined in space group C to R1 = 2.08% on the basis of 4839 unique reflections [Fo > 4σFo]; a = 10.741(6), b = 13.841(8), c = 11.079(6) Å, α = 108.174(6), β = 99.186(6), γ = 89.99(1)°, V = 1542.7(2.7) Å3. Refinement was done using data from a crystal with three twin domains which was part of a grain used for electron probe microanalysis. In the perraultite structure [structure type B1(BG), B – basic, BG – bafertisite group], there is one type of TS (Titanium-Silicate) block and one type of I (Intermediate) block; they alternate along c. The TS block consists of HOH sheets (H – heteropolyhedral, O – octahedral). In the O sheet, the ideal composition of the five [6]MO sites is Mn4apfu. There is no order of Mn and Fe2+ in the O sheet. The MH octahedra and Si2O7 groups constitute the H sheet. The ideal composition of the two [6]MH sites is Ti2apfu. The TS blocks link via common vertices of MH octahedra. The I block contains AP(1,2) and BP(1,2) cation sites. The AP(1) site is occupied by Ba and the AP(2) site by K > Ba; the ideal composition of the AP(1,2) sites is Ba apfu. The BP(1) and BP(2) sites are each occupied by Na > Ca; the ideal composition of the BP(1,2) sites is Na apfu. We compare perraultite and surkhobite based on the work of Sokolova et al. (2020) on the holotype sample of surkhobite: space group C, R1 = 2.85 %, a = 10.728(6), b = 13.845(8), c = 11.072(6) Å, α = 108.185(6), β = 99.219(5), γ = 90.001(8)°, V = 1540.0(2.5) Å3; new EPMA data. We show that (1) perraultite and surkhobite have identical chemical composition and ideal formula NaBaMn4Ti2(Si2O7)2O2(OH)2F; (2) perraultite and surkhobite are isostructural, with no order of Na and Ca at the BP(1,2) sites. Perraultite was described in 1991 and has precedence over surkhobite, which was redefined as “a Ca-ordered analogue of perraultite” in 2008. Surkhobite is not a valid mineral species and its discreditation was approved by CNMNC IMA (IMA 20-A).","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69819821","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}
R. C. Peterson, R. Graham, J. Ervin, I. Kozin, J. Sickman, K. Bozhilov, J. Reid
Sveite [KAl7(NO3)4(OH)16Cl2·8H2O] first described from Venezuela and material recently collected from northern California have similar X-ray diffraction patterns and chemical compositions. The main difference in the chemical composition is the absence of significant chlorine and sulfate in the sveite from California. The changes observed by X-ray diffraction upon hydration and the SEM images of the crystals suggest a layered atomic structure. Water-extractable NO3 in the Venezuelan sveite sample is isotopically enriched in δ15N and δ18O and likely was affected by the microbial process of denitrification. In contrast, the extractable nitrate from the California sveite is less isotopically enriched than the Venezuelan mineral and there is only modest evidence that denitrification had affected its isotopic composition. Overall, the nitrate in the California sveite is isotopically similar to nitrate present in acidic soils overlying the mineral occurrence, suggesting a general biogenic source of uric acid from bird feces for the mineral-bound nitrogen.
{"title":"Sveite from the Northeastern San Joaquin Valley, California","authors":"R. C. Peterson, R. Graham, J. Ervin, I. Kozin, J. Sickman, K. Bozhilov, J. Reid","doi":"10.3749/CANMIN.1900074","DOIUrl":"https://doi.org/10.3749/CANMIN.1900074","url":null,"abstract":"\u0000 Sveite [KAl7(NO3)4(OH)16Cl2·8H2O] first described from Venezuela and material recently collected from northern California have similar X-ray diffraction patterns and chemical compositions. The main difference in the chemical composition is the absence of significant chlorine and sulfate in the sveite from California. The changes observed by X-ray diffraction upon hydration and the SEM images of the crystals suggest a layered atomic structure. Water-extractable NO3 in the Venezuelan sveite sample is isotopically enriched in δ15N and δ18O and likely was affected by the microbial process of denitrification. In contrast, the extractable nitrate from the California sveite is less isotopically enriched than the Venezuelan mineral and there is only modest evidence that denitrification had affected its isotopic composition. Overall, the nitrate in the California sveite is isotopically similar to nitrate present in acidic soils overlying the mineral occurrence, suggesting a general biogenic source of uric acid from bird feces for the mineral-bound nitrogen.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49388169","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. Barkov, L. Bindi, N. Tamura, R. Martin, Chi Ma, B. Winkler, G. Shvedov, W. Morgenroth
Fleetite, Cu2RhIrSb2, a new species of platinum-group mineral (PGM), was discovered intergrown with an Os–Ir–Ru alloy in the Miass Placer Zone (Au–PGE), southern Urals, Russia. A single grain 50 μm across was found. Osmium, ruthenium, and iridium are the main associated minerals; also present are Pt–Fe alloys, laurite, Sb-rich irarsite, Rh-rich tolovkite, kashinite, anduoite, ferronickelplatinum, heazlewoodite, PGE-bearing pentlandite and digenite, as well as micrometric inclusions of forsterite (Fo93.7), chromite–magnesiochromite, and Mg-rich edenite. In reflected light, fleetite is light gray; it is opaque, isotropic, non-pleochroic, and non-bireflectant. We report reflectance values measured in air. A mean of seven point-analyses (wavelength-dispersive spectrometry) gave Cu 13.93, Ni 8.60, Fe 0.10, Ir 28.07, Rh 7.91, Ru 1.96, Sb 39.28, total 99.85 wt.%, corresponding to (Cu1.41Ni0.58Fe0.01)Σ2.00(Rh0.49Ni0.36Ru0.12)Σ0.97Ir0.95Sb2.08 on the basis of six atoms per formula unit, taking into account the structural results. The calculated density is 10.83 g/cm3. Single-crystal X-ray studies show that fleetite is cubic, space group Fdm (#227), a = 11.6682(8) Å, V = 1588.59(19) Å3, and Z = 16. A least-squares refinement of X-ray powder-diffraction data gave a = 11.6575(5) Å and V = 1584.22(19) Å3. The strongest five reflections in the powder pattern [d in Å(I)(hkl)] are: 6.70(75)(111), 4.13(100)(220), 3.52(30)(311), 2.380(50)(422), 2.064(40)(440). Results of synchrotron micro-Laue diffraction experiments are consistent [a = 11.66(2) Å]. The crystal structure of fleetite was solved and refined to R = 0.0340 based upon 153 reflections with Fo > 4σ(Fo). It is isotypic with Pd11Bi2Se2 and best described as intermetallic, with all metal atoms in 12-fold coordination. Fleetite and other late exotic phases were formed by reaction of the associated alloy phases with a fluid phase enriched in Sb, As, and S in circulation in the cooling ophiolite source-rock. The mineral is named after Michael E. Fleet (1938–2017) in recognition of his significant contributions to the Earth Sciences.
{"title":"Fleetite, Cu2RhIrSb2, a New Species of Platinum-Group Mineral from the Miass Placer Zone, Southern Urals, Russia","authors":"A. Barkov, L. Bindi, N. Tamura, R. Martin, Chi Ma, B. Winkler, G. Shvedov, W. Morgenroth","doi":"10.3749/CANMIN.2000073","DOIUrl":"https://doi.org/10.3749/CANMIN.2000073","url":null,"abstract":"\u0000 Fleetite, Cu2RhIrSb2, a new species of platinum-group mineral (PGM), was discovered intergrown with an Os–Ir–Ru alloy in the Miass Placer Zone (Au–PGE), southern Urals, Russia. A single grain 50 μm across was found. Osmium, ruthenium, and iridium are the main associated minerals; also present are Pt–Fe alloys, laurite, Sb-rich irarsite, Rh-rich tolovkite, kashinite, anduoite, ferronickelplatinum, heazlewoodite, PGE-bearing pentlandite and digenite, as well as micrometric inclusions of forsterite (Fo93.7), chromite–magnesiochromite, and Mg-rich edenite. In reflected light, fleetite is light gray; it is opaque, isotropic, non-pleochroic, and non-bireflectant. We report reflectance values measured in air. A mean of seven point-analyses (wavelength-dispersive spectrometry) gave Cu 13.93, Ni 8.60, Fe 0.10, Ir 28.07, Rh 7.91, Ru 1.96, Sb 39.28, total 99.85 wt.%, corresponding to (Cu1.41Ni0.58Fe0.01)Σ2.00(Rh0.49Ni0.36Ru0.12)Σ0.97Ir0.95Sb2.08 on the basis of six atoms per formula unit, taking into account the structural results. The calculated density is 10.83 g/cm3. Single-crystal X-ray studies show that fleetite is cubic, space group Fdm (#227), a = 11.6682(8) Å, V = 1588.59(19) Å3, and Z = 16. A least-squares refinement of X-ray powder-diffraction data gave a = 11.6575(5) Å and V = 1584.22(19) Å3. The strongest five reflections in the powder pattern [d in Å(I)(hkl)] are: 6.70(75)(111), 4.13(100)(220), 3.52(30)(311), 2.380(50)(422), 2.064(40)(440). Results of synchrotron micro-Laue diffraction experiments are consistent [a = 11.66(2) Å]. The crystal structure of fleetite was solved and refined to R = 0.0340 based upon 153 reflections with Fo > 4σ(Fo). It is isotypic with Pd11Bi2Se2 and best described as intermetallic, with all metal atoms in 12-fold coordination. Fleetite and other late exotic phases were formed by reaction of the associated alloy phases with a fluid phase enriched in Sb, As, and S in circulation in the cooling ophiolite source-rock. The mineral is named after Michael E. Fleet (1938–2017) in recognition of his significant contributions to the Earth Sciences.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49042538","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}
S. Barnes, C. Ryan, G. Moorhead, R. Latypov, W. Maier, M. Yudovskaya, B. Godel, L. Schoneveld, M. Vaillant, Mark B. Pearce
The spatial association between Pt minerals, magmatic sulfides, and chromite has been investigated using microbeam X-ray fluorescence (XRF) element mapping and the Maia Mapper. This lab-based instrument combines the Maia parallel energy dispersive (ESD) detector array technology with a focused X-ray beam generated from a liquid metal source. It proves to be a powerful technique for imaging Pt distribution at low-ppm levels on minimally prepared cut rock surfaces over areas of tens to hundreds of square centimeters, an ideal scale for investigating these relationships. Images of a selection of samples from the Bushveld Complex and from the Norilsk-Talnakh ore deposits (Siberia) show strikingly close association of Pt hotspots, equated with the presence of Pt-rich mineral grains, with magmatic sulfide blebs in all cases, except for a taxitic low-S ore sample from Norilsk. In all of the Bushveld samples, at least 75% of Pt hotspots (by number) occur at or within a few hundred microns of the outer edges of sulfide blebs. In samples from the leader seams of the UG2 chromitite, sulfides and platinum hotspots are also very closely associated with the chromite seams and are almost completely absent from the intervening pyroxenite. In the Merensky Reef, the area ratio of Pt hotspots to sulfides is markedly higher in the chromite stringers than in the silicate-dominated lithologies over a few centimeters either side. We take these observations as confirmation that sulfide liquid is indeed the prime collector for Pt and, by inference, for the other platinum group elements (PGEs) in all these settings. We further propose a mechanism for the sulfide-PGE-chromite association in terms of in situ heterogeneous nucleation of all these phases coupled with transient sulfide saturation during chromite growth and subsequent sulfide loss by partial re-dissolution. In the case of the amygdular Norilsk taxite, the textural relationship and high PGE/S ratio is explained by extensive loss of S to an escaping aqueous vapor phase.
{"title":"Spatial Association Between Platinum Minerals and Magmatic Sulfides Imaged with the Maia Mapper and Implications for the Origin of the Chromite-Sulfide-PGE Association","authors":"S. Barnes, C. Ryan, G. Moorhead, R. Latypov, W. Maier, M. Yudovskaya, B. Godel, L. Schoneveld, M. Vaillant, Mark B. Pearce","doi":"10.3749/CANMIN.2000100","DOIUrl":"https://doi.org/10.3749/CANMIN.2000100","url":null,"abstract":"\u0000 The spatial association between Pt minerals, magmatic sulfides, and chromite has been investigated using microbeam X-ray fluorescence (XRF) element mapping and the Maia Mapper. This lab-based instrument combines the Maia parallel energy dispersive (ESD) detector array technology with a focused X-ray beam generated from a liquid metal source. It proves to be a powerful technique for imaging Pt distribution at low-ppm levels on minimally prepared cut rock surfaces over areas of tens to hundreds of square centimeters, an ideal scale for investigating these relationships. Images of a selection of samples from the Bushveld Complex and from the Norilsk-Talnakh ore deposits (Siberia) show strikingly close association of Pt hotspots, equated with the presence of Pt-rich mineral grains, with magmatic sulfide blebs in all cases, except for a taxitic low-S ore sample from Norilsk. In all of the Bushveld samples, at least 75% of Pt hotspots (by number) occur at or within a few hundred microns of the outer edges of sulfide blebs. In samples from the leader seams of the UG2 chromitite, sulfides and platinum hotspots are also very closely associated with the chromite seams and are almost completely absent from the intervening pyroxenite. In the Merensky Reef, the area ratio of Pt hotspots to sulfides is markedly higher in the chromite stringers than in the silicate-dominated lithologies over a few centimeters either side. We take these observations as confirmation that sulfide liquid is indeed the prime collector for Pt and, by inference, for the other platinum group elements (PGEs) in all these settings. We further propose a mechanism for the sulfide-PGE-chromite association in terms of in situ heterogeneous nucleation of all these phases coupled with transient sulfide saturation during chromite growth and subsequent sulfide loss by partial re-dissolution. In the case of the amygdular Norilsk taxite, the textural relationship and high PGE/S ratio is explained by extensive loss of S to an escaping aqueous vapor phase.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43536555","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}
An endmember formula must be: (1) conformable with the crystal structure of the mineral, (2) electroneutral (i.e., not carry a net electric charge), and (3) irreducible [i.e., not capable of being factored into components that have the same bond topology (atomic arrangement) as that of the original formula]. The stoichiometry of an endmember formula must match the “stoichiometry” of the sites in the structure; for ease of expression, I denote such a formula here as a chemical endmember. In order for a chemical endmember to be a true endmember, the corresponding structure must obey the valence-sum rule of bond-valence theory. For most minerals, the chemical endmember and the (true) endmember are the same. However, where local order would lead to strong deviation from the valence-sum rule for some local arrangements, such arrangements cannot occur and the (true) endmember differs from the chemical endmember. I present heuristic and algebraic proofs that a specific chemical formula can always be represented by a corresponding dominant endmember formula. That dominant endmember may be derived by calculating the difference between the mineral formula considered and all of the possible endmember compositions; the endmember formula which is closest to the mineral formula considered is the dominant endmember.
{"title":"Proof That a Dominant Endmember Formula Can Always Be Written for a Mineral or a Crystal Structure","authors":"F. Hawthorne","doi":"10.3749/CANMIN.2000062","DOIUrl":"https://doi.org/10.3749/CANMIN.2000062","url":null,"abstract":"\u0000 An endmember formula must be: (1) conformable with the crystal structure of the mineral, (2) electroneutral (i.e., not carry a net electric charge), and (3) irreducible [i.e., not capable of being factored into components that have the same bond topology (atomic arrangement) as that of the original formula]. The stoichiometry of an endmember formula must match the “stoichiometry” of the sites in the structure; for ease of expression, I denote such a formula here as a chemical endmember. In order for a chemical endmember to be a true endmember, the corresponding structure must obey the valence-sum rule of bond-valence theory. For most minerals, the chemical endmember and the (true) endmember are the same. However, where local order would lead to strong deviation from the valence-sum rule for some local arrangements, such arrangements cannot occur and the (true) endmember differs from the chemical endmember. I present heuristic and algebraic proofs that a specific chemical formula can always be represented by a corresponding dominant endmember formula. That dominant endmember may be derived by calculating the difference between the mineral formula considered and all of the possible endmember compositions; the endmember formula which is closest to the mineral formula considered is the dominant endmember.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46544111","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}
E. Galuskin, I. Galuskina, Biljana Krüger, H. Krüger, Y. Vapnik, A. Krzątała, Dorota Środek, G. Zielinski
The crystal structure of arctite, (Na5Ca)Ca6Ba(PO4)6F3 (Rm, a = 7.904 Å, с = 41.320 Å), was refined in 1984 by E. Sokolova. According to modern concepts, this mineral belongs to the intercalated antiperovskites and is characterized by intercalation of triple antiperovskite layers {[F3(Ca7Na5)](PO4)4}4+ and tetrahedral layers Ba(PO4)24–. The pyrometamorphic rocks of the Hatrurim Complex, which are distributed along the Dead Sea Rift, are the origin of eight new minerals with intercalated antiperovskite structures, all discovered within the last five years. Therefore, an update and improvement of the classification and nomenclature was required. The new classification of the arctite supergroup was approved by the CNMNC IMA (Memorandum 95–SM20). The arctite supergroup combines the arctite group (minerals with triple antiperovskite layers), which includes arctite, (Na5Ca)Ca6Ba(PO4)6F3; nabimusaite, KCa12(SiO4)4(SO4)2O2F; dargaite, BaCa12(SiO4)4(SO4)2O3; and ariegilatite, BaCa12(SiO4)4(PO4)2F2O, with the zadovite group (minerals with single antiperovskite layers), which includes zadovite, BaCa6[(SiO4)(PO4)](PO4)2F; aradite, BaCa6[(SiO4)(VO4)](VO4)2F; gazeevite, BaCa6(SiO4)2(SO4)2O; and stracherite, BaCa6(SiO4)2[(PO4)(CO3)]F. Another ungrouped member of the arctite supergroup is aravaite, Ba2Ca18(SiO4)6[(PO4)3(CO3)]F3O – a unique mineral which is formed by the ordered intercalation of super-modules of ariegilatite and stracherite. In addition, a description of aravaite as a new mineral is presented in this paper. The crystal structure has been previously published (Krüger et al. 2018). Furthermore, preliminary data for potentially new minerals of the arctite supergroup, found in rocks of the Hatrurim Complex, are discussed.
{"title":"Nomenclature and Classification of the Arctite Supergroup.Aravaite, Ba2Ca18(SiO4)6[(PO4)3(CO3)]F3O, a New Arctite Supergroup Mineral from Negev Desert, Israel","authors":"E. Galuskin, I. Galuskina, Biljana Krüger, H. Krüger, Y. Vapnik, A. Krzątała, Dorota Środek, G. Zielinski","doi":"10.3749/CANMIN.2000035","DOIUrl":"https://doi.org/10.3749/CANMIN.2000035","url":null,"abstract":"\u0000 The crystal structure of arctite, (Na5Ca)Ca6Ba(PO4)6F3 (Rm, a = 7.904 Å, с = 41.320 Å), was refined in 1984 by E. Sokolova. According to modern concepts, this mineral belongs to the intercalated antiperovskites and is characterized by intercalation of triple antiperovskite layers {[F3(Ca7Na5)](PO4)4}4+ and tetrahedral layers Ba(PO4)24–. The pyrometamorphic rocks of the Hatrurim Complex, which are distributed along the Dead Sea Rift, are the origin of eight new minerals with intercalated antiperovskite structures, all discovered within the last five years. Therefore, an update and improvement of the classification and nomenclature was required. The new classification of the arctite supergroup was approved by the CNMNC IMA (Memorandum 95–SM20). The arctite supergroup combines the arctite group (minerals with triple antiperovskite layers), which includes arctite, (Na5Ca)Ca6Ba(PO4)6F3; nabimusaite, KCa12(SiO4)4(SO4)2O2F; dargaite, BaCa12(SiO4)4(SO4)2O3; and ariegilatite, BaCa12(SiO4)4(PO4)2F2O, with the zadovite group (minerals with single antiperovskite layers), which includes zadovite, BaCa6[(SiO4)(PO4)](PO4)2F; aradite, BaCa6[(SiO4)(VO4)](VO4)2F; gazeevite, BaCa6(SiO4)2(SO4)2O; and stracherite, BaCa6(SiO4)2[(PO4)(CO3)]F. Another ungrouped member of the arctite supergroup is aravaite, Ba2Ca18(SiO4)6[(PO4)3(CO3)]F3O – a unique mineral which is formed by the ordered intercalation of super-modules of ariegilatite and stracherite. In addition, a description of aravaite as a new mineral is presented in this paper. The crystal structure has been previously published (Krüger et al. 2018). Furthermore, preliminary data for potentially new minerals of the arctite supergroup, found in rocks of the Hatrurim Complex, are discussed.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49489835","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}
Wenqing Huang, P. Ni, Ting Shui, J. Pan, Mingsen Fan, Yulong Yang, Zhe Chi, Jun-ying Ding
Primary rubies in the Ailao Shan of Yunnan Province, China, are found in three layers of marble. However, the origin and source rocks of placer rubies in the Yuanjiang area remains unclear. Trace element geochemistry and inclusion mineralogy within these materials can provide information on their petrogenesis and original source. Zircon, rutile, mica group minerals, titanite, and apatite group minerals were the main solid inclusions identified within the placer Yuanjiang rubies, along with other mineral inclusions such as pyrite, pyrrhotite, plagioclase group minerals, and scapolite group minerals. Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) measurements showed that the placer rubies are characterized by average values of Mg (31 ppmw), Ti (97 ppmw), V (77 ppmw), Cr (3326 ppmw), Fe (71 ppmw), and Ga (66ppmw). A trace-element oxide diagram, Fe values (<350 ppmw), and the mineral inclusion assemblage suggest marble sources for the placer ruby. Therefore, the Yuanjiang rubies (both primary and placer) are metamorphic, and this fits well with the observations that skarn and related minerals are mostly absent in this deposit. Yuanjiang rubies can be readily separated from the high-iron rubies of different geological types by their Fe content (<1000 ppmw). The discriminators Mg, Ga, Cr, V, Fe, and Ti have potential in separating Yuanjiang rubies from some other marble-hosted deposits, such as Snezhnoe. Nevertheless, geographic origin determination remains a challenge when considering the similarities in compositional features between the Yuanjiang rubies and rubies from some other marble-hosted deposits worldwide (e.g., Luc Yen). The presence of kaolinite group minerals and clusters of euhedral, prismatic zircon crystals in ruby suggest a Yuanjiang origin.
{"title":"Trace Element Geochemistry and Mineral Inclusions Constraints on the Petrogenesis of a Marble–Hosted Ruby Deposit in Yunnan Province, China","authors":"Wenqing Huang, P. Ni, Ting Shui, J. Pan, Mingsen Fan, Yulong Yang, Zhe Chi, Jun-ying Ding","doi":"10.3749/CANMIN.2000054","DOIUrl":"https://doi.org/10.3749/CANMIN.2000054","url":null,"abstract":"Primary rubies in the Ailao Shan of Yunnan Province, China, are found in three layers of marble. However, the origin and source rocks of placer rubies in the Yuanjiang area remains unclear. Trace element geochemistry and inclusion mineralogy within these materials can provide information on their petrogenesis and original source. Zircon, rutile, mica group minerals, titanite, and apatite group minerals were the main solid inclusions identified within the placer Yuanjiang rubies, along with other mineral inclusions such as pyrite, pyrrhotite, plagioclase group minerals, and scapolite group minerals. Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) measurements showed that the placer rubies are characterized by average values of Mg (31 ppmw), Ti (97 ppmw), V (77 ppmw), Cr (3326 ppmw), Fe (71 ppmw), and Ga (66ppmw). A trace-element oxide diagram, Fe values (<350 ppmw), and the mineral inclusion assemblage suggest marble sources for the placer ruby. Therefore, the Yuanjiang rubies (both primary and placer) are metamorphic, and this fits well with the observations that skarn and related minerals are mostly absent in this deposit.\u0000 Yuanjiang rubies can be readily separated from the high-iron rubies of different geological types by their Fe content (<1000 ppmw). The discriminators Mg, Ga, Cr, V, Fe, and Ti have potential in separating Yuanjiang rubies from some other marble-hosted deposits, such as Snezhnoe. Nevertheless, geographic origin determination remains a challenge when considering the similarities in compositional features between the Yuanjiang rubies and rubies from some other marble-hosted deposits worldwide (e.g., Luc Yen). The presence of kaolinite group minerals and clusters of euhedral, prismatic zircon crystals in ruby suggest a Yuanjiang origin.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47482302","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}
Frustrated magnetic phases have been a perennial interest to theoreticians wishing to understand the energetics and behavior of quasi-chaotic systems at the quantum level. This behavior also has potentially wide applications to developing quantum data-storage devices. Several minerals are examples of such phases. Since the definition of herbertsmithite, Cu3ZnCl2(OH)6, as a new mineral in 2004 and the rapid realization of the significance of its structure as a frustrated antiferromagnetic phase with a triangular magnetic lattice, there has been intense study of its magnetic properties and those of synthetic compositional variants. In the past five years it has been recognized that the layered copper hydroxyhalides barlowite, Cu4BrF(OH)6, and claringbullite, Cu4FCl(OH)6, are also the parent structures of a family of kagome phases, as they also have triangular magnetic lattices. This paper concerns the structural behavior of claringbullite that is a precursor to the novel frustrated antiferromagnetic states that occur below 30 K in these minerals. The reversible hexagonal (P63/mmc) ↔ orthorhombic (Pnma or Cmcm) structural phase transition in barlowite at 200−270 K has been known for several years, but the details of the structural changes that occur through the transition have been largely unexplored, with the focus instead being on quantifying the low-temperature magnetic behavior of the orthorhombic phase. This paper reports the details of the structural phase transition in natural claringbullite at 100−293 K as studied by single-crystal X-ray diffraction. The transition temperature has been determined to lie between 270 and 293 K. The progressive disordering of Cu at the unusual trigonal prismatic Cu(OH)6 site on heating is quantified through the phase transition for the first time, and a methodology for refining this disorder is presented. Key changes in the behavior of Cu(OH)4Cl2 octahedra in claringbullite have been identified that suggest why the Pnma structure is likely stabilized over an alternative Cmcm structure. It is proposed that the presence of a non-centrosymmetric octahedron in the Pnma structure allows more effective structural relaxation during the phase transition than can be achieved by the Cmcm structure, which has only centrosymmetric octahedra.
{"title":"The Hexagonal ↔ Orthorhombic Structural Phase Transition in Claringbullite, Cu4FCl(OH)6","authors":"M. Welch, J. Najorka, M. Rumsey, J. Spratt","doi":"10.3749/CANMIN.2000041","DOIUrl":"https://doi.org/10.3749/CANMIN.2000041","url":null,"abstract":"\u0000 Frustrated magnetic phases have been a perennial interest to theoreticians wishing to understand the energetics and behavior of quasi-chaotic systems at the quantum level. This behavior also has potentially wide applications to developing quantum data-storage devices. Several minerals are examples of such phases. Since the definition of herbertsmithite, Cu3ZnCl2(OH)6, as a new mineral in 2004 and the rapid realization of the significance of its structure as a frustrated antiferromagnetic phase with a triangular magnetic lattice, there has been intense study of its magnetic properties and those of synthetic compositional variants. In the past five years it has been recognized that the layered copper hydroxyhalides barlowite, Cu4BrF(OH)6, and claringbullite, Cu4FCl(OH)6, are also the parent structures of a family of kagome phases, as they also have triangular magnetic lattices. This paper concerns the structural behavior of claringbullite that is a precursor to the novel frustrated antiferromagnetic states that occur below 30 K in these minerals. The reversible hexagonal (P63/mmc) ↔ orthorhombic (Pnma or Cmcm) structural phase transition in barlowite at 200−270 K has been known for several years, but the details of the structural changes that occur through the transition have been largely unexplored, with the focus instead being on quantifying the low-temperature magnetic behavior of the orthorhombic phase. This paper reports the details of the structural phase transition in natural claringbullite at 100−293 K as studied by single-crystal X-ray diffraction. The transition temperature has been determined to lie between 270 and 293 K. The progressive disordering of Cu at the unusual trigonal prismatic Cu(OH)6 site on heating is quantified through the phase transition for the first time, and a methodology for refining this disorder is presented. Key changes in the behavior of Cu(OH)4Cl2 octahedra in claringbullite have been identified that suggest why the Pnma structure is likely stabilized over an alternative Cmcm structure. It is proposed that the presence of a non-centrosymmetric octahedron in the Pnma structure allows more effective structural relaxation during the phase transition than can be achieved by the Cmcm structure, which has only centrosymmetric octahedra.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2021-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48337955","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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