DOCSLIB.ORG

Barringer Crater Stishovite: Oxygen-18 Rich Relative to Bulk Target Rock; J.F

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Barringer Crater Stishovite: Oxygen-18 Rich Relative to Bulk Target Rock; J.F 756 LPSC XIX BARRINGER CRATER STISHOVITE: OXYGEN-18 RICH RELATIVE TO BULK TARGET ROCK; J.F. McHone and L.P. Knauth, Dept. of Geology, Arizona State University, Tempe AZ 85287-1604 We have measured 6180 for samples of stishovite, coesite, and whole-rock shocked and unshocked Coconino Sandstone from Barringer (Meteor) Crater, Arizona. In analyses from this study and from published whole-rock data (I), stishovite is distinctly enriched in 018 by about 2 0100 relative to all other samples. SUMMARY OF 6180 (doo SMOW) DATA COCONINO SANDSTONE, METEOR CRATER ARlZONA Previous Study' 6'80 Whole-rock, Normal, Unshocked 1 2.8 Whole-rock, Normal, Unshocked 1 2.9 Whole-rock, Lightly Shocked 13.0 Whole-rock, Lightly Shocked 13.0 Whole-rock, Moderately Shocked 1 3.8 Whole-rock, Strongly Shocked 12.6 Whole-rock, Strongly Shocked 12.5 Whole-rock, Frothy Glass 12.6 Whole-rock, Frothy Glass 12.5 This Study Whole-rock, Normal, Unshocked 13.6 Whole-rock, Moderately Shocked 1 2.8 Whole-rock, Frothy Glass 12.8 Coesite 13.2 Coesite 13.2 Stishovite + Coesite 13.7 Stishovite + Coesite 13.7 Stishovite 15.4 Stishovite 15.0 Stishovite 15.1 *After Taylor & Epstein, (ref.1 ) Two possible mechanisms might produce anomolous 6180 values in stishovite: 1) a previously unrecognised form of isotope shock fractionation or 2) formation of stishovite by selective shock metamorphism of a quartz component having an original 0181dhtio different from that of bulk Coconino Sandstone. Kieffer (2) and Kieffer et al. (3) reported individual grains of Coconino Sandstone commonly exhibit pre-impact quartz cement overgrowths. They observed that stishovite occured only at grain boundaries and suggested that it formed by direct nucleation from host quartz rather than crystallization from hot silica melts as did the more abundant coesite. Overgrowths on detrital quartz form at sedimentary temperatures and are therefore enriched in 6180 relative to the igneous-metamorphic quartz originally deposited as clastic sediment. If stishovite forms preferentially in quartz overgrowths, it should be richer in 6180 than samples of whole-rock, as observed. O Lunar and Planetary Institute Provided by the NASA Astrophysics Data System LPSC XIX 757 STISHOVITE: OXYGEN-18 RICH McHone, JF. and LP. Knauth Porous, sedimentary rocks respond somewhat differently to an impact event than do solid, crystalline targets (4,5,6). Peak pressure pulses due to passage of a shock wave through a porous medium, such as a sandstone, are thought to be concentrated near edges of colliding grain boundaries. In contrast, pressure pulses passing through solid crystalline rocks, such as a granite, are more uniformly distributed; coesite and stishovite form as minute aggregates in crystallographicaly controled lamellae within individual quartz grains. We suggest stishovite at Meteor Crater was derived selectively from quartz overgrowth cements and that the observed stishovite 6180 enrichment relative to bulk Coconino is a result of shock-wave pressures concentrated near grain boundaries in a porous, sedimentary target rock. Acknowledgements: The writers express gratitude to the following Arizona State University staff : Sarah L. Kealy provided isotope analyses, Charles F. Lewis prepared coesite and stishovite separates, Dr. A. Yates performed X-ray diffraction powder analyses, and Dr. R. A. Nieman performed nuclear magnetic resonance analyses. A grant from the Barringer Crater Company, Princeton, NJ, provided partial support for J.F.M. References: 1) Taylor, H.P.,Jr. and Epstein, S., 1969. J. Geophys. Res., vol. 74, no. 23, p.6834- 6844. 2) Kieffer, S.W., 1971. J. Geophys. Res., vol. 76, no.23, p.5449-5473. 3) Kieffer, S.W., P. P. Phakey, and J.M. Christie, 1976. Cont. Min. Petrol., vol. 59, p.41- 93. 4)Stoffler, D., 197 1. J. Geophys. Res., vo1.76, no.23, p.5474-5488. 5) Robertson, B.P., 1980. Lunar and Planet. Sci. Conf.11 th, p.929-934. 6) Schaal, R.B., F. Horz, T.D. Thompson, and J.F. Baur, 1979. Proc. Lunar Sci. Conf., loth, p.2547-2571. O Lunar and Planetary Institute Provided by the NASA Astrophysics Data System .
Load more

Recommended publications
  • Terrestrial Impact Structures Provide the Only Ground Truth Against Which Computational and Experimental Results Can Be Com­ Pared
    Ann. Rev. Earth Planet. Sci. 1987. 15:245-70 Copyright([;; /987 by Annual Reviews Inc. All rights reserved TERRESTRIAL IMI!ACT STRUCTURES ··- Richard A. F. Grieve Geophysics Division, Geological Survey of Canada, Ottawa, Ontario KIA OY3, Canada INTRODUCTION Impact structures are the dominant landform on planets that have retained portions of their earliest crust. The present surface of the Earth, however, has comparatively few recognized impact structures. This is due to its relative youthfulness and the dynamic nature of the terrestrial geosphere, both of which serve to obscure and remove the impact record. Although not generally viewed as an important terrestrial (as opposed to planetary) geologic process, the role of impact in Earth evolution is now receiving mounting consideration. For example, large-scale impact events may hav~~ been responsible for such phenomena as the formation of the Earth's moon and certain mass extinctions in the biologic record. The importance of the terrestrial impact record is greater than the relatively small number of known structures would indicate. Impact is a highly transient, high-energy event. It is inherently difficult to study through experimentation because of the problem of scale. In addition, sophisticated finite-element code calculations of impact cratering are gen­ erally limited to relatively early-time phenomena as a result of high com­ putational costs. Terrestrial impact structures provide the only ground truth against which computational and experimental results can be com­ pared. These structures provide information on aspects of the third dimen­ sion, the pre- and postimpact distribution of target lithologies, and the nature of the lithologic and mineralogic changes produced by the passage of a shock wave.
    [Show full text]
  • Stishovite and Seifertite in Lunar Meteorite Northwest Africa 4734
    71st Annual Meteoritical Society Meeting (2008) 5058.pdf FIRST EVIDENCE OF HIGH PRESSURE SILICA: STISHOVITE AND SEIFERTITE IN LUNAR METEORITE NORTHWEST AFRICA 4734. H. Chennaoui Aoudjehane1-2, A. Jambon2 1Université Hassan II Aïn Chock, Laboratoire Géosciences, BP 5366 Maârif Casa- blanca Morocco (e-mail: [email protected]), 2Université Pierre et Marie Curie-Paris6 and IPGP Laboratoire MAGIE, Case 110, 4 place Jussieu, 75252 Paris France. Introduction: Silica is a rare phase in lunar rocks; it has been described as either quartz, cristobalite and/or tridymite [1]. Northwest Africa 4734, is an uncommon type of lunar rock, which may be launched paired with the LaPaz Icefield Lunar Mare basalts found in 2002-03 in Antarctica [2-6], it is a coarse grained rock of basaltic composition, exhibits a number of sig- nificant shock features, such as PDFs, extensive fracturation of pyroxene, impact melt pockets and transformation of plagioclase to maskelynite; silica is present as a minor phase. Analytical procedures: We studied the speciation of silica polymorphs to characterize the shock, using SEM imaging, Ra- man spectroscopy, CL imaging and spectroscopy. Further details can be found in [7]. Results: According to the CL spectra [7-9], cristobalite, tridymite, high-pressure silica glass, stishovite and seifertite, are all present. Special emphasis is made on stishovite and seifertite, which, like in shergottites, exhibit specific textural features [7]. Cathodoluminescence spectra characteristic of high-pressure sil- ica phases: glass, stishovite and seifertite have been recorded in addition to the original low-pressure phases. The remanence of cristobalite and tridymite underscores a significant heterogeneity of the shock supported by the rock.
    [Show full text]
  • EPSC2018-833, 2018 European Planetary Science Congress 2018 Eeuropeapn Planetarsy Science Ccongress C Author(S) 2018
    EPSC Abstracts Vol. 12, EPSC2018-833, 2018 European Planetary Science Congress 2018 EEuropeaPn PlanetarSy Science CCongress c Author(s) 2018 Impact melt boulder from northern Sweden from an unknown source Timmu Kreitsmann (1), Satu Hietala (2), Tapio Soukka (3), Jüri Plado (1), Jari Nenonen (2) and Lauri J. Pesonen (4) (1) Department of Geology, University of Tartu, Estonia ([email protected], [email protected]), (2) Geological Survey of Finland, Finland ([email protected], [email protected]), (3) Oulu Mining School, University of Oulu, Finland ([email protected]) (4) Solid Earth Geophysics Laboratory, Physics Department, University of Helsinki, Finland ([email protected]) Abstract We report an impact melt rock finding from northern Sweden, near the village of Kitkiöjärvi. There is no confirmed meteorite impact structure nearby, thus, the source is currently undiscovered. The impact origin of the finding was confirmed by the presence of planar deformation features (PDFs) in quartz. 1. Introduction Impact cratering is a common and frequent process that affects the planetary surfaces across the solar system throughout geologic time. On Earth, there are 191 confirmed impact structures which are distributed unevenly around the globe. The Fennoscandian Shield houses around 10% of them. Here, we report an impact melt rock finding that originates from an unknown structure in northern Sweden. The semi-rounded impactite boulder, sized 10 × 7 cm, was found by Tapio Soukka in 2017 from a gravel pit at the western side of village Kitkiöjärvi (67°46'16"N 23°03'06"E; Fig. 1). Figure 1: Proven impact structures in Fennoscandia.
    [Show full text]
  • A New Way to Confirm Meteorite Impact Produced Planar Features in Quartz: Combining Universal Stage and Electron Backscatter Diffraction Techniques
    A new way to confirm meteorite impact produced planar features in quartz: combining Universal Stage and Electron Backscatter Diffraction techniques M.H. Voorn MSc Thesis August 2010 Utrecht University - Earth Sciences department Structural Geology and Tectonic research group Abstract As recognised from the geological record, meteorite impact events can have a severe influence on (local) geology, climate and life. Solid evidence for these events is therefore important to obtain. The most convincing evidence comes from microstructures in quartz. Upon impact, Planar Fractures (PFs) and Planar Deformation Features (PDFs) form parallel to specific crystallographic planes in quartz. Non-impact formed (tectonic) Deformation Lamellae (DL) may be hard to distinguish qualitatively from PFs or PDFs with the optical microscope, but do not form parallel to crystallographic planes. Quantitative methods using the Universal Stage (U-Stage) on the optical microscope have therefore been applied widely to (dis)confirm this parallelism. With the method, the quartz c-axis and poles to planar features are measured and plotted. An improved technique requires so-called indexing of the measured orientations using a stereographic projection template. Even when these techniques are applied, some proposed impact structures remain debated. An important reason for this is the U-stage can not provide the full crystal orientation of quartz. The goal of this thesis was to check the classical U-stage techniques for quantitatively confirming impact planar features in quartz, and to see whether the addition of Electron Backscatter Diffraction (EBSD, on the Scanning Electron Microscope: SEM) and Cathodoluminescence (CL, on the SEM) can provide more solid evidence. Six previously confirmed impact and three non-impact samples were studied.
    [Show full text]
  • ANIC IMPACTS: MS and IRONMENTAL P ONS Abstracts Edited by Rainer Gersonde and Alexander Deutsch
    ANIC IMPACTS: MS AND IRONMENTAL P ONS APRIL 15 - APRIL 17, 1999 Alfred Wegener Institute for Polar and Marine Research Bremerhaven, Germany Abstracts Edited by Rainer Gersonde and Alexander Deutsch Ber. Polarforsch. 343 (1999) ISSN 01 76 - 5027 Preface .......3 Acknowledgements .......6 Program ....... 7 Abstracts P. Agrinier, A. Deutsch, U. Schäre and I. Martinez: On the kinetics of reaction of CO, with hot Ca0 during impact events: An experimental study. .11 L. Ainsaar and M. Semidor: Long-term effect of the Kärdl impact crater (Hiiumaa, Estonia) On the middle Ordovician carbonate sedimentation. ......13 N. Artemieva and V.Shuvalov: Shock zones on the ocean floor - Numerical simulations. ......16 H. Bahlburg and P. Claeys: Tsunami deposit or not: The problem of interpreting the siliciclastic K/T sections in northeastern Mexico. ......19 R. Coccioni, D. Basso, H. Brinkhuis, S. Galeotti, S. Gardin, S. Monechi, E. Morettini, M. Renard, S. Spezzaferri, and M. van der Hoeven: Environmental perturbation following a late Eocene impact event: Evidence from the Massignano Section, Italy. ......21 I von Dalwigk and J. Ormö Formation of resurge gullies at impacts at sea: the Lockne crater, Sweden. ......24 J. Ebbing, P. Janle, J, Koulouris and B. Milkereit: Palaeotopography of the Chicxulub impact crater and implications for oceanic craters. .25 V. Feldman and S.Kotelnikov: The methods of shock pressure estimation in impacted rocks. ......28 J.-A. Flores, F. J. Sierro and R. Gersonde: Calcareous plankton stratigraphies from the "Eltanin" asteroid impact area: Strategies for geological and paleoceanographic reconstruction. ......29 M.V.Gerasimov, Y. P. Dikov, 0 . I. Yakovlev and F.Wlotzka: Experimental investigation of the role of water in the impact vaporization chemistry.
    [Show full text]
  • Twinning, Reidite, and Zro in Shocked Zircon from Meteor Crater
    Transformations to granular zircon revealed: Twinning, reidite, and ZrO2 in shocked zircon from Meteor Crater (Arizona, USA) Aaron J. Cavosie1,2,3, Nicholas E. Timms1, Timmons M. Erickson1, Justin J. Hagerty4, and Friedrich Hörz5 1TIGeR (The Institute for Geoscience Research), Department of Applied Geology, Curtin University, Perth, WA 6102, Australia 2NASA Astrobiology Institute, Department of Geoscience, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA 3Department of Geology, University of Puerto Rico–Mayagüez, Mayagüez, Puerto Rico 00681, USA 4U.S. Geological Survey (USGS) Astrogeology Science Center, Flagstaff, Arizona 86001, USA 5NASA Johnson Space Center, Science Department/Jets/HX5/ARES, Houston, Texas 77058, USA ABSTRACT Granular zircon in impact environments has long been recognized but remains poorly A N35° 2.0’ W111° 0.9’ understood due to lack of experimental data to identify mechanisms involved in its genesis. Meteor Crater in Arizona (USA) contains abundant evidence of shock metamorphism, includ- N ing shocked quartz, the high-pressure polymorphs coesite and stishovite, diaplectic SiO2 glass, and lechatelierite (fused SiO2). Here we report the presence of granular zircon, a new shocked-mineral discovery at Meteor Crater, that preserve critical orientation evidence of specific transformations that occurred during formation at extreme impact conditions. The zircon grains occur as aggregates of sub-micrometer neoblasts in highly shocked Coconino Sandstone (CS) comprised of lechatelierite. Electron backscatter diffraction shows that each MCC2 site grain consists of multiple domains, some with boundaries disoriented by 65° around <110>, (main shaft) a known {112} shock-twin orientation. Other domains have {001} in alignment with {110} of neighboring domains, consistent with the former presence of the high-pressure ZrSiO4 polymorph reidite.
    [Show full text]
  • Meteorite Impacts, Earth, and the Solar System
    Traces of Catastrophe A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures Bevan M. French Research Collaborator Department of Mineral Sciences, MRC-119 Smithsonian Institution Washington DC 20560 LPI Contribution No. 954 i Copyright © 1998 by LUNAR AND PLANETARY INSTITUTE The Institute is operated by the Universities Space Research Association under Contract No. NASW-4574 with the National Aeronautics and Space Administration. Material in this volume may be copied without restraint for library, abstract service, education, or personal research purposes; however, republication of any portion thereof requires the written permission of the Insti- tute as well as the appropriate acknowledgment of this publication. Figures 3.1, 3.2, and 3.5 used by permission of the publisher, Oxford University Press, Inc. Figures 3.13, 4.16, 4.28, 4.32, and 4.33 used by permission of the publisher, Springer-Verlag. Figure 4.25 used by permission of the publisher, Yale University. Figure 5.1 used by permission of the publisher, Geological Society of America. See individual captions for reference citations. This volume may be cited as French B. M. (1998) Traces of Catastrophe:A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures. LPI Contribution No. 954, Lunar and Planetary Institute, Houston. 120 pp. This volume is distributed by ORDER DEPARTMENT Lunar and Planetary Institute 3600 Bay Area Boulevard Houston TX 77058-1113, USA Phone:281-486-2172 Fax:281-486-2186 E-mail:[email protected] Mail order requestors will be invoiced for the cost of shipping and handling. Cover Art.“One Minute After the End of the Cretaceous.” This artist’s view shows the ancestral Gulf of Mexico near the present Yucatán peninsula as it was 65 m.y.
    [Show full text]
  • Global Catastrophes in Earth History
    GLOBAL CATASTROPHES IN EARTH HISTORY An Interdisciplinary Conference on Impacts, Volcanism, and Mass Mortality Snowbird, Utah October 20-23, 1988 N89-2 12E7 --?HEW- Sponsored by The Lunar and Planetary Institute and The National Academy of Sciences Abstracts Presented to the Topical Conference Global Catastrophes in Earth History: An Interdisciplinary Conference on Impacts, Volcanism, and Mass Mortality Snowbird, Utah October 20 - 23,1988 Sponsored by Lunar and Planetary Institute and The National Academy of Sciences LPI Contribution No. 673 Compiled in 1988 Lunar and Planetary Institute Material in this volume may be copied without restraint for library, abstract service, educational, or personal research purposes; however, republication of any paper or portion thereof requires the written permission of the authors as well as appropriate acknowledgment of this publication. PREFACE This volume contains abstracts that have been accepted for presentation at the topical conference Global Catastrophes in Earth History: An Interdisciplinary Conference on Impacts, Volcanism and Mass Mortality. The Organizing Committee consisted of Robert Ginsburg, Chairman, University of Miami; Kevin Burke, Lunar and Planetary Institute; Lee M. Hunt, National Research Council; Digby McLaren, University of Ottawa; Thomas Simkin, National Museum of Natural History; Starley L. Thompson, National Center for Atmospheric Research; Karl K. Turekian, Yale University; George W. Wetherill, Carnegie Institution of Washington. Logistics and administrative support were provided by the Projects Ofice at the Lunar and Planetary Institute. This abstract volume was prepared by the Publications Office staff at the Lunar and Planetary Institute. The Lunar and Planetary Institute is operated by the Universities Space Research Association under contract No. NASW-4066 with the National Aeronautics and Space Administration.
    [Show full text]
  • FORTY YEARS of MICROTEKTITE RESEARCH. B. P. Glass. Geology Department, University of Delaware, New- Ark, DE 19716, USA
    68th Annual Meteoritical Society Meeting (2005) 5006.pdf FORTY YEARS OF MICROTEKTITE RESEARCH. B. P. Glass. Geology Department, University of Delaware, New- ark, DE 19716, USA. E-mail: [email protected]. I first heard of tektites when I took Brian Mason’s geochem- istry course in 1965. Shortly thereafter, I found some glass beads, which I concluded must be microtektites related to the Australasian tektites, in five sediment cores from the Indian Ocean [1]. I then searched for and found Ivory Coast microtek- tites in cores from the eastern equatorial Atlantic Ocean [2]. Bill Cassidy obtained some compositional data, which helped confirm the identification of the microtektites [e.g., 3]. After this, I searched for North American (N.A.) microtektites, but before I could find them, Donnelly and Chao [4] reported finding them in an upper Eocene sediment core from the Caribbean Sea. Using biostratigraphic data from that core, we were able to find the N.A. microtektite layer in additional cores. We then discovered clinopyroxene-bearing (cpx) spherules associated with the N.A. microtektites. This layer was found to be associated with an Ir anomaly [5] and with the extinction of several radiolarian taxa. We traced the cpx spherule layer across the equatorial Pacific Ocean and into the eastern equatorial Indian Ocean. We first thought that the N.A. strewn field extended across the Pacific Ocean and into the Indian Ocean, but we later concluded that the cpx spherules belong to an older event. N.A. microtektites were then discovered in marine sediments on Barbados [6], and, so far, this is the only place where microtektites have been found on land.
    [Show full text]
  • Shock Metamorphism of the Coconino Sandstone At
    SHOCK METAMORPHISM OF THE COCONINO SANDSTONE AT METEOR CRATER By susan w. Kieffer At Meteor Crater the Coconino Sandstone was metamorphosed by ex­ tremely high pressures and temperatures associated with the impact of the meteorite . The unshocked sandstone and the textural and mineralogical changes recognized in shocked samples are described below . The features described are illustrated in Figures 5 and 6. Unshocked Sandstone The Coconino Sandstone (named by Darton, 1910) underlies 32,000 square miles of the Colorado Plateau province in northern Arizona, extend­ ing south to the Mogollon cliffs and west to the Grand Wash cliffs. It is exposed as far east as Holbrook, Arizona, and thins to apparent ex­ tinction near the Utah border, but probably grades laterally into the DeChelly Formation in the north (Baker and Reeside, 1929) . At Meteor Crater, outcrops of Coconino Sandstone are best seen on the east wall, but small outcrops also occur on the north, west, and south walls . The nearest exposures outside of the crater are 24 km (15 miles) to the south. The sandstone attains a maximum thickness of 330 m (1000 feet) at its southern extent. The Coconino Sandstone, as exposed in the Grand Canyon, was first described by Noble (1914) . He described wedge- shaped units of pale buff, fine~grained, crossbedded sandstone whose distinctive features are the huge scale of the crossbedding, the massive appearance and the uniform fineness of the component grains of sand . The wedge-shaped units often exceed 40 feet in length and 100 feet in height. The dip of the bedding planes in a southern direction is commonly 15° to 25° , or exceptionally, 30°.
    [Show full text]
  • An Unusual Occurrence of Coesite at the Lonar Crater, India
    Meteoritics & Planetary Science 52, Nr 1, 147–163 (2017) doi: 10.1111/maps.12745 An unusual occurrence of coesite at the Lonar crater, India 1* 1 2 1 3 Steven J. JARET , Brian L. PHILLIPS , David T. KING JR , Tim D. GLOTCH , Zia RAHMAN , and Shawn P. WRIGHT4 1Department of Geosciences, Stony Brook University, Stony Brook, New York 11794–2100, USA 2Department of Geosciences, Auburn University, Auburn, Alabama 36849, USA 3Jacobs—NASA Johnson Space Center, Houston, Texas 77058, USA 4Planetary Science Institute, Tucson, Arizona 85719, USA *Corresponding author. E-mail: [email protected] (Received 18 March 2016; revision accepted 06 September 2016) Abstract–Coesite has been identified within ejected blocks of shocked basalt at Lonar crater, India. This is the first report of coesite from the Lonar crater. Coesite occurs within SiO2 glass as distinct ~30 lm spherical aggregates of “granular coesite” identifiable both with optical petrography and with micro-Raman spectroscopy. The coesite+glass occurs only within former silica amygdules, which is also the first report of high-pressure polymorphs forming from a shocked secondary mineral. Detailed petrography and NMR spectroscopy suggest that the coesite crystallized directly from a localized SiO2 melt, as the result of complex interactions between the shock wave and these vesicle fillings. INTRODUCTION Although there is no direct observation of nonshock stishovite in nature, a possible post-stishovite phase may High-Pressure SiO2 Phases be a large component of subducting slabs and the core- mantle boundary (Lakshtanov et al. 2007), and Silica (SiO2) polymorphs are some of the simplest stishovite likely occurs in the deep mantle if basaltic minerals in terms of elemental chemistry, yet they are slabs survive to depth.
    [Show full text]
  • Moldavite-12-2001.Pdf
    Cdbdladq1//0RsnmdnesgdLnmsg9Lnkc`uhsd Scientists have concluded that about 15 million years ago, a meteorite more than half a mile wide crashed violently into southern Germany. In a fraction of a second, surface rocks were melted and thrown a couple hundred miles into the western Czech Republic! We invite you to read of the discovery of the origin of our mysterious moldavites. OGXRHB@K OQNODQSHDR Chemistry: High silica content with oxides of calcium, aluminum, iron, and magnesium Class: Not a mineral. Natural Glass Group: Tektite Crystal System: None, amorphous Habits: Usually small; scarred surfaces and irregular shapes Color: Lime green to olive green, bottle-green to brown, occasionally bicolor Luster: Vitreous to dull Transparency: Translucent to transparent Streak: White Refractive Index: 1.48-1.52 Cleavage: None Fracture: Conchoidal; Brittle Hardness: 5.5 Specific Gravity: 2.34-2.4 Luminescence: No reaction to ultraviolet light, but exhibits a yellow-green glow under X-rays Distinctive Features and Tests: Characteristic shapes, Scarring; Color; Unique localities M @L D Pronounced m4l!-da-vt, the name comes from the Moldau river in the Czech Republic. After World War II, the Czechs called the river Vltava, (Moldau is a German word,) and the moldavites “vltavites.” The name does not come from the territory of Moldavia, which is now part of Romania. When biologist Joseph Mayer of the Charles University in Prague first described these unique stones in 1788, he named them “chrysolites,” and they have also been called pseudochrysolites, water chrysolites, and bottlestones (German bouteillenstein.) Fortunately, the name chrysolite did not stick, as it would probably have led to confusion, as chrysolite is from the Greek word khrysolithos, meaning “gold stone,” and was used in ancient times to denote any yellow-colored gem, and now refers to olivine of a yellow- green color, or is sometimes used in the gem trade to describe yellow, transparent chrysoberyl.
    [Show full text]