MEROHEDRAL TWINNING IN THE ZEOLITE PHlLLIPSITE AND THE FORMATION OF MERLINOITE DOMAINS MARK HOWARD BADHAM A thesis submitted to the Department of Geological Sciences in conformity with the requirernents for the degree Master of Science Queen's University Kingston, Ontario, Canada September 1997 Copyright O Mark Howard Badham, September 1997 National Library Bibliothèque nationale of Canada du Canada Acquisitions and Acquisitions et Bibtiographic Services services bibliographiques 395 Wellington Street 395. nie Wellington OttawaON K1AON4 Ottawa ON K1A ON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in microfonn, vendre des copies de cette thèse sous paper or electronic formats. la forme de rnicrofiche/nlm, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fkom it Ni la thèse ni des extraits subsîantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation, i A bstract A zeolite from Cava Nuova, Monte Somma, Vesuvio, Italy, origindy identified as the rare mineral merlinoite &Ca&3&Si,0a)-24H,0, has been studied by powder and single- crystal X-ray diffraction, optical microscopy, and electron micro probe. The powder pattern shows d-space iines unique to meriinoite at - 10A and -4.45A, however, it also shows d-spacings that are found only in the structurally similar mineral phillipsite (YNa,Ca),,(Si,Al)gO,~ 6H20.Precession work reveals that the reciprocal lattice of this sample matches the stmcture of phillipsite that is merohedraily twinned. The twin law has been identifieci as a 90' rotation about the a axis as illustrated by the morphology of the crystals; the precession-film lattice patterns; and indirectly by the fact that the crystal structure could not be refined from CAD4 difEiactometer data collected during the study. It is postulated that twlluiing in this phillipsite is responsible for the formation of merlinoite domains within the ciystal. In phillipsite, the siliwn/aiuminurn tetrahedra are linked to form incomplete doublarings in a sinusoidd or "wavy" ribbon structure. The merlinoite fiarnework is similar, except that it is based on complete double-rings. It is shown that at twin boundaries in the sarnple being studied, complete rings could form, and that repetitive twinnllig results in the exact merlinoite structure. ii The formation of rnerlinoite in phillipsite by twinnuig has implications for the vaiidity of thermodynamic data calculateci in 1990 for synthetic merlinoite. The produas of the synthesis were reported as merlinoite and zeolite ZK-19 (a syithetic phiiiipsite-like phase) that were identsed by powder pattern alone. Since ZK-19 does not have the -6.4A line of normal phillipsite, it would be very difncult by powder diaction alone to distinguish pure merlinoite fiom an intergrowth of twinned ZX- 19 and merlinoite. The thermodynarnic data calculated may therefore be based on a compound which is not pure merlinoite. iii Acknowledgements The author would like to thank several people who have helped him during the long, drawn-out process of completing a part-time Master's Degree. First and foremost, I would Wce to thank my wife, Sheryl, who never gave up on me and constantly offered me encouragement to wry on with this study. This work is dedicated to her, and to my daughter Torie whose life began almost at the same tirne as this project did all those years ago. My supervisor, Dr. R. C. Peterson, always had helpful suggestions when problems arose, and he was understanding when my farnily and my niIl-the job often occupied more of my time than my research did. Alan Grant kept the X-ray equipment operating, and on more than one occasion went out of his way to make sure 1had the equipment cor@prations that 1 needed to complete this study. Thanks are also due to Forrest Cureton of Tucson, Arizona, who supplied the sample. This research was supported by an National Science and Engineering Research Councii gant to Dr R.C. Peterson. iv Table of Contents v References ___CI -- - Appendices Appendk 1: Merlinoite Stmcture Refinement Files: LATCON Appendii II: Theorectical D-spacings for Phillipsite - Appendix III: Microprobe Analyses with Balance Error Calculations -- -_HI-_- Vita------- - -_---_ List of Tables Table 1: Powder Pattern of Analcime Cornpareci to JCPDS Card #4 1- 1478 -____- ----_ Table 2: Powder Pattern of Dioside Compared to JCPDS Card #Il-654-------- -------O-- Table 3 : Powder Pattern of Ankerite and Calcite wmpared To JCPDS Cards #3 3-282 and #5-586------- Table 4: Merlinoite: Gandolfi and Difractometer X-ray Cornparison---- List of Figures Figure 2- 1: The Double Crankshaft Structure--------------- 5 Figure 2-2: The Crystal Structure of Merboite-- ------- 8 Figure 2-3 : The Crystal Structure of Phillipsite- -- O--- 10 Figure 2-4: Schematic Cornparison of Merlinoite and PhiMipsite Structures----- ----pu---i-------- 12 vi Figure 2-5: Unit Cell Choices in Philiipsite- Figure 3-1: Whole-rock X-ray Powder Pattern Figure 4- 1: Gandolfi X-ray Powder Patterns of Sample Figure 4-2: X-ray Powder Diffiactometer Trace of Sample Figure 4-3 : Zero-level Precession Film Indexed with the Merlinoite CeU. Figure 4-4: Cone Axis Film ---- Figure 4-5: Upper-Ievel Precession Film Indexed with the Merlinoite CeU- - Figure 46: Zero-level Precession Film Indexed with the Phillipsite Ceii Figure 4-7: Upper-level Film Indexed with the Phillipsite Ceii -_---- Figure 4-8: Cornparison of Precession Films Taken at Right Angles------- Figure 4-9: Reciprocal Lattice Points Due to Twinning----- Figure 4- 10: Phillipsite Crystal Morphology Diagrams- -- Figure 4- 1 1: Photomicrograp h of Crystal ------ Figure 5- 1: Electron Back-scatter Images of Microprobe Samples Showing Analysis Areas - Figure 6- 1: Twinning Causing Merlinoite Domains in Philii psite------ Figure 6-2: Photomicrograph Down a Showing Complex Twinnùig---- -1- Chapter 1. Scope and Purpose of Study This study focuses on a sarnple wntaining smd (Clmrn) glassy translucent crystals reportedly identifiai by X-ray difidion as the rare zeoiite merlinoite (Forrest Cureton, personal communication) fiom a new locaiity at Cava Nuova, Monte Somma, Vesuvio, Napoli, Itaiy. These samples are currently being marketed by several mineral dealers as "particularly fine crystais of merlinoite that are much better than the type locality material." Preliminary Gandoln X-ray dfiaction studies on this sarnple by Vaiyashko and McGlade (unpublished course work, 1995) did show key lines at 10A and 4.47A that are essential in identifjmg merlinoite, but several other lines were also present in the pattern which can not be indexed using the merlinoite space group and ceii. Precession photos also showed anornaIous difEaction spots, and extinction conditions that are not consistent with the Immm space group assigneci to merlinoite. Due to the weii-developed nature of the crystals in this sample, a çhidy was initiated to investigate the crystallography and fùrther refine the crystal structure of merlinoite. The ultirnate goal at the outset of this project was to explain the extra Iines in the powder difEaction pattern and the precession photo anomalies by either assigning a new space group and redefining the crystal structure, or by identifjmg a new mineral species. Methods of investigation employed in this work include X-ray powder difiaction, single- -2- crystal d-action ( CAD4 automated difEactometer, and Buerger precession carnera), electron micro probe, and optical microsco py and goniometry. -3- Chapter 2. Literature Review 2.1 History and Significance of Zeolite-group Minerals Natural zeoiite-group rninerals are characterized by a three-diensional dumino-silicate fiamework (tektosilicates) with open channels in the structure containing loosely-bound water molecules and exchangeable cations (Gottardi and Galli, 1985). Today, they are known fiom many geological environments, notably of hydrothermal origin in volcanic rocks and as microcrystalline masses formed by rock-water chernical reactions in rocks of volcanic-sedimentary origin. The first use of the narne "zeolite", which loosely translates from its Greek root words as "boiling stone", dates back to Cronstedt, 1756, who used the tem to describe minerals which expel water when heated (Gottardi and Gdi, 1985). One of the rernarkable and economically useful features of zeolites is that this expulsion of water is reversible, as the mineral readily re-hydrates at room temperature with no structural changes. In fact, this property is essential for a minera1 to be included in the zeolite group. More irnportantly fiom a commercial viewpoint, dehydrated (or "activated") zeolites will adsorb not only water but a variety of other molecules by a process coined "molecular sieving" by McBain in 1932 (Mumpton, 1977). In the 1950's the study of zeoiite-like phases began in emest when their industrial applications as ion exchangers and molecular sieves were recognized. Much of the research today centres on synthetic phases that are tailored as specific molecular sieves. -4- Although there are roughly 30-40 natural zeolites known,