DOCSLIB.ORG

GENETIC MINERALOGY of the BURBANKITE GROUP Yulia V

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
GENETIC MINERALOGY of the BURBANKITE GROUP Yulia V 50 New Data on Minerals. M., 2004. Vol. 39 UDC 549.742 GENETIC MINERALOGY OF THE BURBANKITE GROUP Yulia V. Belovitskaya Geological Faculty, Lomonosov Moscow State University, Moscow, Russia, [email protected] Igor V. Pekov Geological Faculty, Lomonosov Moscow State University, Moscow, Russia, [email protected] The burbankite group consists of six mineral species with general formula А3В3(СО3)5 where А = Na > Ca, REE3+, ; B = Sr, Ca, Ba, REE3+, Na: burbankite, khanneshite, calcioburbankite, remondite(Ce), remon- dite(La), and petersenite(Ce). The burbankite structural type (space group P63mc) is exclusively stable for chemical composition variations: khanneshite, calcioburbankite, remondite hexagonal analogue, and bur- bankite are isostructural and form the system of continous solid solutions. All chemical compositions (94 analyses) of the burbankite group minerals can be described within the isomorphous system with end mem- 2+ 2+ bers: (Na2Ca)М 3(CO3)5 and Na3(REE2Na)(CO3)5, where М =Sr, Ba, Ca. There are three genetic types of the burbankite mineralization: 1) in carbonatites where the minerals with the “most averaged” chemical composi- tion and increased contents of Ba and Ca are formed; 2) in alkaline hydrothermalites where the range of chem- ical compositions of the burbankitelike phases is extremely wide; 3) in pectolite metasomatites where bur- bankite is strongly REEdepleted. In carbonatites the burbankite group minerals are early phases formed under hightemperature conditions, whereas in nepheline syenite massifs they are formed during hydrother- mal stages under low temperatures, which is due to different regime of CO2. Under alkalinity decrease the bur- bankite group minerals are replaced by a whole series of secondary minerals, among which the alkalifree car- bonates of REE, Sr, Ba, and Ca prevail. 5 tables, 3 figures, 50 references. The burbankite group consists of six miner- colours: yellow, green, palebrown, pink. Fre - al species with general formula А3В3(СО3)5 quently colorless and white, less often red, where А = Na > Ca, REE3+,; B = Sr, Ca, Ba, orange and gray varieties occur. 3+ REE , Na: burbankite (Na,Ca, )3 (Sr,REE, Ba, Burbankite is a widespread mineral, where- Ca)3 (СО3)5, khanneshite (Na,Ca)3(Ba,Sr, REE,Ca)3 as other members of the group are rare. In one (СО3)5, calcioburbankite (Na,Ca,REE)3 (Ca,REE, of types of «rareearth carbonatites» (Khibiny, Sr)3 (СО3)5, remondite(Ce) Na3(Ce,Ca,Na,Sr)3 Vuoriyarvi, Gornoe Ozero etc.) burbankite and (СО3)5, remondite(La) Na3(La,Ce,Ca)3(СО3)5, its alteration products will form huge accumu- and petersenite(Ce) (Na,Ca)4(Ce,La,Sr)2 (СО3)5. lations, being the main potentially industrial The first three minerals are hexagonal (space component and easily enriched complex ore of gro up P63mc), and others are pseudohexagonal REE, Sr, and Ba. monoclinic (sp. gr. P21, g = 119.8–120.5°). In spite of a semicentennial history of In the crystal structures of hexagonal mem- research, significant number of the publica- bers of this group there are two independent tions, and extensive geography of finds, gener- cationic sites — А (Na и Са) and В (REE, Sr, Ba alizing papers on the burbankite group miner- и Са), and three types of carbonate groups with als are absent. We have attempted to system- different orientations. Tenvertex Bpolyhedra atize earlier published materials and having connected to CO3groups by vertices form the supplemented them with comparable volume layers of sixmember rings parallel (001). of new data to show the connection of chemical Eightvertex Apolyhedra form infinite zigzag composition and structural features of these columns where neighboring polyhedra are minerals with conditions of their formiation. contacted by planes (Voronkov, Shumyats ka ya, We have studied 32 samples from eight alka- 1968; Effenberger et al., 1985; Belovitskaya et al., line complexes — Khibiny, Lovozero (Kola Pe - 2000, 2001, 2002). The crystal structure of n insula), Vuoriyarvi (Northen Kareliya), Vish - remondite is quite similar to that of burbankite ne vye Gory (Southern Urals), Gornoe Ozero, (Ginderow, 1989). In the crystal structure of Mu r un (East Siberia), Mont SaintHilaire (Que - petersenite atoms of Na occupy with order two bec, Canada), and Khanneshin (Afgha nistan). Bpolyhedra out of six, which results to dou- The cation composition of the minerals bling of aparameter (Grice et al., 1994). (Tables 1–3) was studied by electronmicro- Burbankite group carbonates form hexago- probe method. All analyses including refer- nal prismatic crystals but occur more often as ence data were calculated on charge sum equal irregular grains and their aggregates. These 10.00, i.e. equivalent (CO3)5. Bsite was filled up minerals are transparent, without cleavage, to 3.00 atoms per formula unit (apfu) by atoms have vitreous up to greasy luster and light of Sr, Ba, REE, Th, K, in case of their deficiency Genetic mineralogy of the burbankite group 51 by atoms of Ca, and then atoms of Na was REEdepleted burbankite, connected to specif- added. After that the rest of Na and Ca atoms ic pectolite metasomatites of Khibiny and was placed in Asite. If the Acations sum ap - Murun massifs. In each case the minerals are peared less 3.00, the missing value was attrib- cha racterized by individual features of cation uted to vacancy according to the crystalloche - ratios (Fig. 1). Burbankite from sodabearing mi cal data (Effenberger et al., 1985; Be lov it - sedimentary Green River Formation (USA) is in skaya et al., 2000). At calculation the atomic association with the majority of the same miner- mass of Ce is conditionally taken for old analy- als as in carbonatites and alkaline hydrother- ses where the rareearth elements were deter- malites (Fitzpatrick, Pabst, 1977) and, probably, mined as a sum. The cation composition of the has lowtemperature hydrothermal origin. burbankite group minerals widely varies (Fig. Occurrences of the burbankite group minerals 1, 2). In Asites, sodium always prevails (1.3– with known chemical composition are briefly des - 3 apfu), but sometimes amounts of calcium is cribed in Table 5. They are grouped for genetic also essential (up to 1.25 apfu). The cation com- types. Localities connected to rocks enclosing car- position is more diverse in Bsites where atoms bonatites and also with products of hydrothermal of Sr, Ba, Ce, La, and Ca can dominate. activity in carbonatites are conditionally referred We make the Xray powder studies for 11 to carbonatite type. The finds made in late parage- samples (Table 4) including five species with neses of pegmatite from nepheline syenite com- different chemical composition, which crystal plex are referred to alkaline hydrothermalites. structures was refined by Rietveld method: Thus, burbankite group minerals are formed in 1) REEdepleted burbankite (an. 92), its Xray alkalicarbonate systems connected to geological diffraction pattern contains distinct doublets; objects of different types. The temperature range 2) burbankite with «typical» composition (an. these minerals crystallize in is extremely wide. 64) and nonsplit peaks on Xray spectrum; A number of massifs contain carbonatites whe- 3) khanneshite (an. 21); 4) calcioburbankite re the burbankite group minerals are the main (an. 12); 5) the mineral with chemical composi- concentrators of strontium, barium, and raree - tion of re mondite(Ce) (an. 79), but according arth elements. Here burbankite and its analogs to its Xray powder diagram identical to repre- crystallize on early carbonatite formation stages sentatives of the burbankite structural type. under high temperatures (not below 500°С). That Burbankite group minerals form complex confirmed by the signs of joint growth with essen- isomorphous system with end members: tial minerals of carbonatite rocks, the presence of 2+ REEfree phases (Na2Ca)М 3(CO3)5 where the burbankite group minerals in primary inclu- М2+ = Sr, Ba, Ca and petersenite sions, and the replacement of these minerals by Na3(REE2Na)(СО3)5, without divalent cations. products of later hydrotermal stages. All chemical compositions of the minerals are In alkaline hydrothermalites the burbankite situated in interval between these two points group minerals are the late formations forming forming extended field — Fig 1, and 2a, b. In at essentially lower temperatures. Their crys- spite of two structural transitions: from hexago- tals in cavities are frequently observed togeth- nal members to mo noclinic remondite and then to er with zeolites and hydrous soda minerals. petersenite, essential mixable intermissions in this Formation temperatures for these associations system aren’t determined. These structural transi- can be estimated as 100–250°С. tions are concerned to the second type, i.e. they The difference in time of crystallization are are realized gradually, without break of chemical first of all connected to different regime of car- bonds. bon dioxide. The excess of CO2 is present in car- bonatite formation systems, and already at early stages burbankite and its analogs appear under Occurrences and formation conditions sufficient activity of sodium. In nepheline syen- Generalizing an available material, it was ite massifs, with which the burbankitebearing possible to distinguish three main genetic types hydrothermalites are in general connected, of burbankite mineralization. Each of them is increase of potential of CO2 and, accordingly, connected to alkaline rocks. The lar gest bur- the development of carbonate mineralization bankite concentrations occur in carbonatites. take place mainly on a final stage of evolution This genetic type is studied better then others. In alkaline hydrothermalites the widest varia- tions of chemical compositions and, according- Typochemism ly, the greatest species variety are observed at and structural typomorphism relatively small amounts. We have distingu is - The wide variations of cation composition hed the third genetic type, accumulations of ma ke the burbankite group minerals very in - 52 New Data on Minerals. M., 2004. Vol. 39 a b c FIG. 1. Cation ratios in the burbankite group minerals: a — from carbonatites, b — from alkaline hydrothermalites, c — from pectolite metasomatites formative in genetic relation.
Load more

Recommended publications
  • Mineral Processing
    Mineral Processing Foundations of theory and practice of minerallurgy 1st English edition JAN DRZYMALA, C. Eng., Ph.D., D.Sc. Member of the Polish Mineral Processing Society Wroclaw University of Technology 2007 Translation: J. Drzymala, A. Swatek Reviewer: A. Luszczkiewicz Published as supplied by the author ©Copyright by Jan Drzymala, Wroclaw 2007 Computer typesetting: Danuta Szyszka Cover design: Danuta Szyszka Cover photo: Sebastian Bożek Oficyna Wydawnicza Politechniki Wrocławskiej Wybrzeze Wyspianskiego 27 50-370 Wroclaw Any part of this publication can be used in any form by any means provided that the usage is acknowledged by the citation: Drzymala, J., Mineral Processing, Foundations of theory and practice of minerallurgy, Oficyna Wydawnicza PWr., 2007, www.ig.pwr.wroc.pl/minproc ISBN 978-83-7493-362-9 Contents Introduction ....................................................................................................................9 Part I Introduction to mineral processing .....................................................................13 1. From the Big Bang to mineral processing................................................................14 1.1. The formation of matter ...................................................................................14 1.2. Elementary particles.........................................................................................16 1.3. Molecules .........................................................................................................18 1.4. Solids................................................................................................................19
    [Show full text]
  • Adamsite-(Y), a New Sodium–Yttrium Carbonate Mineral
    1457 The Canadian Mineralogist Vol. 38, pp. 1457-1466 (2000) ADAMSITE-(Y), A NEW SODIUM–YTTRIUM CARBONATE MINERAL SPECIES FROM MONT SAINT-HILAIRE, QUEBEC JOEL D. GRICE§ and ROBERT A. GAULT Research Division, Canadian Museum of Nature, P.O. Box 3443, Station D, Ottawa, Ontario K1P 6P4, Canada ANDREW C. ROBERTS Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada MARK A. COOPER Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada ABSTRACT Adamsite-(Y), ideally NaY(CO3)2•6H2O, is a newly identified mineral from the Poudrette quarry, Mont Saint-Hilaire, Quebec. It occurs as groups of colorless to white and pale pink, rarely pale purple, flat, acicular to fibrous crystals. These crystals are up to 2.5 cm in length and form spherical radiating aggregates. Associated minerals include aegirine, albite, analcime, ancylite-(Ce), calcite, catapleiite, dawsonite, donnayite-(Y), elpidite, epididymite, eudialyte, eudidymite, fluorite, franconite, gaidonnayite, galena, genthelvite, gmelinite, gonnardite, horváthite-(Y), kupletskite, leifite, microcline, molybdenite, narsarsukite, natrolite, nenadkevichite, petersenite-(Ce), polylithionite, pyrochlore, quartz, rhodochrosite, rutile, sabinaite, sérandite, siderite, sphalerite, thomasclarkite-(Y), zircon and an unidentified Na–REE carbonate (UK 91). The transparent to translucent mineral has a vitreous to pearly luster and a white streak. It is soft (Mohs hardness 3) and brittle with perfect {001} and good {100} and {010} cleav- ␣ ␤ ␥ ° ° ages. Adamsite-(Y) is biaxial positive, = V 1.480(4), = 1.498(2), = 1.571(4), 2Vmeas. = 53(3) , 2Vcalc. = 55 and is nonpleochroic. Optical orientation: X = [001], Y = b, Z a = 14° (in ␤ obtuse). It is triclinic, space group P1,¯ with unit-cell parameters refined from powder data: a 6.262(2), b 13.047(6), c 13.220(5) Å, ␣ 91.17(4), ␤ 103.70(4), ␥ 89.99(4)°, V 1049.1(5) Å3 and Z = 4.
    [Show full text]
  • Infrare D Transmission Spectra of Carbonate Minerals
    Infrare d Transmission Spectra of Carbonate Mineral s THE NATURAL HISTORY MUSEUM Infrare d Transmission Spectra of Carbonate Mineral s G. C. Jones Department of Mineralogy The Natural History Museum London, UK and B. Jackson Department of Geology Royal Museum of Scotland Edinburgh, UK A collaborative project of The Natural History Museum and National Museums of Scotland E3 SPRINGER-SCIENCE+BUSINESS MEDIA, B.V. Firs t editio n 1 993 © 1993 Springer Science+Business Media Dordrecht Originally published by Chapman & Hall in 1993 Softcover reprint of the hardcover 1st edition 1993 Typese t at the Natura l Histor y Museu m ISBN 978-94-010-4940-5 ISBN 978-94-011-2120-0 (eBook) DOI 10.1007/978-94-011-2120-0 Apar t fro m any fair dealin g for the purpose s of researc h or privat e study , or criticis m or review , as permitte d unde r the UK Copyrigh t Design s and Patent s Act , 1988, thi s publicatio n may not be reproduced , stored , or transmitted , in any for m or by any means , withou t the prio r permissio n in writin g of the publishers , or in the case of reprographi c reproductio n onl y in accordanc e wit h the term s of the licence s issue d by the Copyrigh t Licensin g Agenc y in the UK, or in accordanc e wit h the term s of licence s issue d by the appropriat e Reproductio n Right s Organizatio n outsid e the UK. Enquirie s concernin g reproductio n outsid e the term s state d here shoul d be sent to the publisher s at the Londo n addres s printe d on thi s page.
    [Show full text]
  • Carbon Mineral Ecology: Predicting the Undiscovered Minerals of Carbon
    American Mineralogist, Volume 101, pages 889–906, 2016 Carbon mineral ecology: Predicting the undiscovered minerals of carbon ROBERT M. HAZEN1,*, DANIEL R. HUMMER1, GRETHE HYSTAD2, ROBERT T. DOWNS3, AND JOSHUA J. GOLDEN3 1Geophysical Laboratory, Carnegie Institution, 5251 Broad Branch Road NW, Washington, D.C. 20015, U.S.A. 2Department of Mathematics, Computer Science, and Statistics, Purdue University Calumet, Hammond, Indiana 46323, U.S.A. 3Department of Geosciences, University of Arizona, 1040 East 4th Street, Tucson, Arizona 85721-0077, U.S.A. ABSTRACT Studies in mineral ecology exploit mineralogical databases to document diversity-distribution rela- tionships of minerals—relationships that are integral to characterizing “Earth-like” planets. As carbon is the most crucial element to life on Earth, as well as one of the defining constituents of a planet’s near-surface mineralogy, we focus here on the diversity and distribution of carbon-bearing minerals. We applied a Large Number of Rare Events (LNRE) model to the 403 known minerals of carbon, using 82 922 mineral species/locality data tabulated in http://mindat.org (as of 1 January 2015). We find that all carbon-bearing minerals, as well as subsets containing C with O, H, Ca, or Na, conform to LNRE distributions. Our model predicts that at least 548 C minerals exist on Earth today, indicating that at least 145 carbon-bearing mineral species have yet to be discovered. Furthermore, by analyzing subsets of the most common additional elements in carbon-bearing minerals (i.e., 378 C + O species; 282 C + H species; 133 C + Ca species; and 100 C + Na species), we predict that approximately 129 of these missing carbon minerals contain oxygen, 118 contain hydrogen, 52 contain calcium, and more than 60 contain sodium.
    [Show full text]
  • Mineral Index
    Mineral Index Abhurite T.73, T.355 Anandite-Zlvl, T.116, T.455 Actinolite T.115, T.475 Anandite-20r T.116, T.45S Adamite T.73,T.405, T.60S Ancylite-(Ce) T.74,T.35S Adelite T.115, T.40S Andalusite (VoU, T.52,T.22S), T.27S, T.60S Aegirine T.73, T.30S Andesine (VoU, T.58, T.22S), T.41S Aenigmatite T.115, T.46S Andorite T.74, T.31S Aerugite (VoU, T.64, T.22S), T.34S Andradite T.74, T.36S Agrellite T.115, T.47S Andremeyerite T.116, T.41S Aikinite T.73,T.27S, T.60S Andrewsite T.116, T.465 Akatoreite T.73, T.54S, T.615 Angelellite T.74,T.59S Akermanite T.73, T.33S Ankerite T.74,T.305 Aktashite T.73, T.36S Annite T.146, T.44S Albite T.73,T.30S, T.60S Anorthite T.74,T.415 Aleksite T.73, T.35S Anorthoclase T.74,T.30S, T.60S Alforsite T.73, T.325 Anthoinite T.74, T.31S Allactite T.73, T.38S Anthophyllite T.74, T.47S, T.61S Allanite-(Ce) T.146, T.51S Antigorite T.74,T.375, 60S Allanite-(La) T.115, T.44S Antlerite T.74, T.32S, T.60S Allanite-(Y) T.146, T.51S Apatite T.75, T.32S, T.60S Alleghanyite T.73, T.36S Aphthitalite T.75,T.42S, T.60 Allophane T.115, T.59S Apuanite T.75,T.34S Alluaudite T.115, T.45S Archerite T.75,T.31S Almandine T.73, T.36S Arctite T.146, T.53S Alstonite T.73,T.315 Arcubisite T.75, T.31S Althausite T.73,T.40S Ardaite T.75,T.39S Alumino-barroisite T.166, T.57S Ardennite T.166, T.55S Alumino-ferra-hornblende T.166, T.57S Arfvedsonite T.146, T.55S, T.61S Alumino-katophorite T.166, T.57S Argentojarosite T.116, T.45S Alumino-magnesio-hornblende T.159,T.555 Argentotennantite T.75,T.47S Alumino-taramite T.166, T.57S Argyrodite (VoU,
    [Show full text]
  • Alphabetical List
    LIST L - MINERALS - ALPHABETICAL LIST Specific mineral Group name Specific mineral Group name acanthite sulfides asbolite oxides accessory minerals astrophyllite chain silicates actinolite clinoamphibole atacamite chlorides adamite arsenates augite clinopyroxene adularia alkali feldspar austinite arsenates aegirine clinopyroxene autunite phosphates aegirine-augite clinopyroxene awaruite alloys aenigmatite aenigmatite group axinite group sorosilicates aeschynite niobates azurite carbonates agate silica minerals babingtonite rhodonite group aikinite sulfides baddeleyite oxides akaganeite oxides barbosalite phosphates akermanite melilite group barite sulfates alabandite sulfides barium feldspar feldspar group alabaster barium silicates silicates albite plagioclase barylite sorosilicates alexandrite oxides bassanite sulfates allanite epidote group bastnaesite carbonates and fluorides alloclasite sulfides bavenite chain silicates allophane clay minerals bayerite oxides almandine garnet group beidellite clay minerals alpha quartz silica minerals beraunite phosphates alstonite carbonates berndtite sulfides altaite tellurides berryite sulfosalts alum sulfates berthierine serpentine group aluminum hydroxides oxides bertrandite sorosilicates aluminum oxides oxides beryl ring silicates alumohydrocalcite carbonates betafite niobates and tantalates alunite sulfates betekhtinite sulfides amazonite alkali feldspar beudantite arsenates and sulfates amber organic minerals bideauxite chlorides and fluorides amblygonite phosphates biotite mica group amethyst
    [Show full text]
  • A Specific Gravity Index for Minerats
    A SPECIFICGRAVITY INDEX FOR MINERATS c. A. MURSKyI ern R. M. THOMPSON, Un'fuersityof Bri.ti,sh Col,umb,in,Voncouver, Canad,a This work was undertaken in order to provide a practical, and as far as possible,a complete list of specific gravities of minerals. An accurate speciflc cravity determination can usually be made quickly and this information when combined with other physical properties commonly leads to rapid mineral identification. Early complete but now outdated specific gravity lists are those of Miers given in his mineralogy textbook (1902),and Spencer(M,i,n. Mag.,2!, pp. 382-865,I}ZZ). A more recent list by Hurlbut (Dana's Manuatr of M,i,neral,ogy,LgE2) is incomplete and others are limited to rock forming minerals,Trdger (Tabel,l,enntr-optischen Best'i,mmungd,er geste,i,nsb.ildend,en M,ineral,e, 1952) and Morey (Encycto- ped,iaof Cherni,cal,Technol,ogy, Vol. 12, 19b4). In his mineral identification tables, smith (rd,entifi,cati,onand. qual,itatioe cherai,cal,anal,ys'i,s of mineral,s,second edition, New york, 19bB) groups minerals on the basis of specificgravity but in each of the twelve groups the minerals are listed in order of decreasinghardness. The present work should not be regarded as an index of all known minerals as the specificgravities of many minerals are unknown or known only approximately and are omitted from the current list. The list, in order of increasing specific gravity, includes all minerals without regard to other physical properties or to chemical composition. The designation I or II after the name indicates that the mineral falls in the classesof minerals describedin Dana Systemof M'ineralogyEdition 7, volume I (Native elements, sulphides, oxides, etc.) or II (Halides, carbonates, etc.) (L944 and 1951).
    [Show full text]
  • Chemical Staining Methods Used in the Identification of Carbonate Minerals
    CHEMICAL STAINING METHODS USED IN THE IDENTIFICATION OF CARBONATE MINERALS Tamer AYAN Mineral Research and Exploration Institute of Turkey INTRODUCTION Carbonate minerals are the major constituents of sedimentary rocks; however, they are also found in igneous and metamorphic rocks, either as primary or as secondary minerals. In carbonate rocks formed either by chemical or mechanical deposition, these minerals constitute the main rock-forming components. Sometimes they are also found in great abundance in pelitic, psammitic and psephitic rocks. According to their crystallographic characteristics, carbonate minerals may be subdivided into two main groups : 1) Calcite group : Hexagonal-rhombohedral system. 2) Aragonite group : Orthorhombic system «pseudohexagonal». Of the calcite group of minerals, calcite (CaCO3) and dolomite [CaMg (CO3)2] are the two minerals which are dominantly found in sediments. Depending on its purity, or iron and magnesium content, calcite may be found in states of pure calcite, ferro-calcite, or slightly to abundantly magnesian calcite. Similarly, according to the iron content percentage, dolomite may also be regarded as having been composed of two end members, pure dolomite and ferrous dolomite, in varying proportions. The other calcite group minerals are ankerite «ferroferric dolomite» [CaFe(CO3)2], magnesite (MgCO3), siderite (FeCO3), smithsonite (ZnCO3), rhodochrosite (MnCO3) and spherocobaltite (CoC03). The most important mineral of the aragonite group is aragonite (CaCO3); the others, in decreasing order of importance, are witherite (BaCO3), strontianite (SrCO3), cerussite (PbCO3) and alstonite [(Ba, Ca)CO3]. Apart from their refractive indexes (R.I.), the optical and crystallographic characteristics of carbonate minerals are very similar to each other. Therefore identification of carbonates on hand specimens or even in thin sections, is rather difficult.
    [Show full text]
  • The Crystal Structure of Alstonite, Baca(CO3)2: an Extraordinary Example of ‘Hidden’ Complex Twinning in Large Single Crystals
    Mineralogical Magazine (2020), 84, 699–704 doi:10.1180/mgm.2020.61 Article The crystal structure of alstonite, BaCa(CO3)2: an extraordinary example of ‘hidden’ complex twinning in large single crystals Luca Bindi1* , Andrew C. Roberts2 and Cristian Biagioni3 1Dipartimento di Scienze della Terra, Università di Firenze, Via G. La Pira 4, I-50121 Firenze, Italy; 2Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada; and 3Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria 53, I-56126 Pisa, Italy Abstract Alstonite, BaCa(CO3)2, is a mineral described almost two centuries ago. It is widespread in Nature and forms magnificent cm-sized crystals. Notwithstanding, its crystal structure was still unknown. Here, we report the crystal-structure determination of the mineral and discuss it in relationship to other polymorphs of BaCa(CO3)2. Alstonite is trigonal, space group P31m, with unit-cell parameters 3 a = 17.4360(6), c = 6.1295(2) Å, V = 1613.80(9) Å and Z = 12. The crystal structure was solved and refined to R1 = 0.0727 on the σ c basis of 4515 reflections with Fo >4 (Fo) and 195 refined parameters. Alstonite is formed by the alternation, along , of Ba-dominant and Ca-dominant layers, separated by CO3 groups parallel to {0001}. The main take-home message is to show that not all structure determinations of minerals/compounds can be solved routinely. Some crystals, even large ones displaying excellent diffraction quality, can be twinned in complex ways, thus making their study a crystallographic challenge. Keywords: alstonite, carbonate, barium, calcium, crystal structure, twinning (Received 11 June 2020; accepted 25 July 2020; Accepted Manuscript published online: 29 July 2020; Associate Editor: Charles A Geiger) Introduction b = 17.413(5), c = 6.110(1) Å and β = 90.10(1)°, with a unit-cell volume 12 times larger than the orthorhombic cell proposed by Alstonite, BaCa(CO ) , is polymorphous with barytocalcite, para- 3 2 Gossner and Mussgnug (1930).
    [Show full text]
  • Witherite Composition, Physical Properties, and Genesis
    American Mineralogist, Volume 64, pages 742-747, 1979 Witherite composition,physical properties,and genesis ARTHUR BaTDRSARI' AND J. ALnxaNonn SpBen Orogenic Studies Laboratory, Department of Geological Sciences Virginia Polytechnic Institute and State University B lacksburg, Virginia 2406 I Abstract Microprobe analysesof 17 natural witherite specimensfrom various localities show sub- stitution of strontium (up to I I mole percent),lesser amounts of calcium ( < I mole percent) and no detectiblelead. Most witheritescontain lessthan 4 mole percentSr and 0.5 mole per- cent Ca. Lattice parametersand density vary regularly with compositionin the entire range. The equation,equivalent mole percentSrCO, (+l.l): -1102.58(drro,A) + 2515.74,can be used to determinethe approximatecomposition of witherite-strontianite solid solutions for X(SrCO3)< I L A plot of mean ionic radius ys.cell volume for natural witheriteslies above the plane connectingthe pure end-membersBaCOr-SrCOr-CaCOr, suggesting a small posi- tive excessvolume of mixing. Calcium substitution 1slimited to minor amounts becauseof the miscibility gap between witherite and orthorhombic CaBa(COr)r,alstonite. The limited Sr substitutionand negligible Pb substitution,however, are believed to depend upon the composition of the pre-existing sulfate (barite) from which witherite forms and the disequilibrium behavior of low-temper- ature solutions(<200'C) that crystallizeorthorhombic carbonates. Introduction mated ARL SEMQmicroprobe at 15 kV and l0 This work is part of a systematic study of the nanoamps,employing Bence-Albeemethods of data chemistry and physical properties of the ortho- reduction. Standardsincluded synthetic BaCOr(Ba) rhombic carbonates.The probable conditions and and SrCOr(Sr)and natural calcite (Ca) and cerussite mechanismsof witherite genesisare examinedin or- (Pb).
    [Show full text]
  • Volume 66, 1981*
    INDEX, VOLUME 66, 1981* Ab jnixio M0 calculations 819,1237 Analyses, cont. Analyses,cont. 'l233 974 Achondrite, oriented olivine ec1og i ie 459 zoisite, Cr epi dote, Cr 974 ANDERS0N,C.S. and S.t^l. BAILEY: ACKERMAND,DIETRICH see pattern FRANZ,GERHARD 872 eugsteri te A newcation ordering 185 Acrofanite, newmineral (abstr) I'r00 fayal i te 95 in amesite-2az Adu.laria,analyses 484 Fe dolomite 51? ANDERSON,J.B. sEeSHOEMAKER, 485 forsteri te 498 G.L. 169 Aegirine, analyses genesis 938 Afghanite, structure 777 fri edeli te I 061 Andesite,experirnental garnet 463,7lI ,743,1027 Anilite, Cu-Sbond 813 Ajoite, newdata 201 phase AKIZUKI,MIZUHIK0: Investigation glasses, Na 547 Anorthite, equilibria ll83 of phase transition of natural graphitic sulfidic schists 916 Antaractica greenali te az5 meteoriticolivine I 233 ZnSminerals by high resolu- '1006 to22 tion electron microscopy halloysite r 004 surinamite,etc. 480 Antigorite, dissolution 801 _: Origin of optical heulandi te variation in analcime 403 hypersthene 75,337 Apatite Albi te i I menite 95,728,978 analyses 670 analys es 484 iron formation 89,51 1 inclusionin Cr diopside 347 heat capacity 1202 jonsomervilleite 834 Apuanite, microstructure I 073 Aldermanite,new mineral (abstr) 1099 kanoite 128 Aragonite,oolite 789 ARAKI.TAKAHARU and P.B. M00RE: Alforsite, newmineral 1050 kaolinite rock I 004 - Alkali diffusion, EPMA 547 kar'l i te 875 Diieni te, cul+Mn?tFe3l(oH)6 kornerupine 743 (Asrt03)5(Si lr04J i(Asr+04 ) : Alkali feldspars, thennodynamic t+; functi ons 1202 kutnahorite 280 metallic (AslrCu clusters Alkremite, Utah 741 kyani te 706 in an oxide matrix 1263 ALLARD,L.F.
    [Show full text]
  • Download PDF About Minerals Sorted by Mineral Group
    MINERALS SORTED BY MINERAL GROUP Most minerals are chemically classified as native elements, sulfides, sulfates, oxides, silicates, carbonates, phosphates, halides, nitrates, tungstates, molybdates, arsenates, or vanadates. More information on and photographs of these minerals in Kentucky is available in the book “Rocks and Minerals of Kentucky” (Anderson, 1994). NATIVE ELEMENTS (DIAMOND, SULFUR, GOLD) Native elements are minerals composed of only one element, such as copper, sulfur, gold, silver, and diamond. They are not common in Kentucky, but are mentioned because of their appeal to collectors. DIAMOND Crystal system: isometric. Cleavage: perfect octahedral. Color: colorless, pale shades of yellow, orange, or blue. Hardness: 10. Specific gravity: 3.5. Uses: jewelry, saws, polishing equipment. Diamond, the hardest of any naturally formed mineral, is also highly refractive, causing light to be split into a spectrum of colors commonly called play of colors. Because of its high specific gravity, it is easily concentrated in alluvial gravels, where it can be mined. This is one of the main mining methods used in South Africa, where most of the world's diamonds originate. The source rock of diamonds is the igneous rock kimberlite, also referred to as diamond pipe. A nongem variety of diamond is called bort. Kentucky has kimberlites in Elliott County in eastern Kentucky and Crittenden and Livingston Counties in western Kentucky, but no diamonds have ever been discovered in or authenticated from these rocks. A diamond was found in Adair County, but it was determined to have been brought in from somewhere else. SULFUR Crystal system: orthorhombic. Fracture: uneven. Color: yellow. Hardness 1 to 2.
    [Show full text]