Occurrence and Distribution of Moganite and Opal-CT in Agates from Paleocene/Eocene Tuffs, El Picado (Cuba)

Total Page:16

File Type:pdf, Size:1020Kb

Occurrence and Distribution of Moganite and Opal-CT in Agates from Paleocene/Eocene Tuffs, El Picado (Cuba) minerals Article Occurrence and Distribution of Moganite and Opal-CT in Agates from Paleocene/Eocene Tuffs, El Picado (Cuba) Jens Götze 1,*, Klaus Stanek 2, Gerardo Orozco 3 , Moritz Liesegang 4 and Tanja Mohr-Westheide 5 1 Institute for Mineralogy, TU Bergakademie Freiberg, Brennhausgasse 14, 09599 Freiberg, Germany 2 Institute for Geology, TU Bergakademie Freiberg, Cottastraße 4, 09599 Freiberg, Germany; [email protected] 3 Departamento de Geología, Universidad de Moa, Avenida Calixto Garcia Iñiguez 15, Moa, Holguín 83330, Cuba; [email protected] 4 Institute for Geological Sciences, FU Berlin, Malteserstraße 74–100, 12249 Berlin, Germany; [email protected] 5 Institute for Evolution and Biodiversity Science, Museum für Naturkunde, Invalidenstraße 43, 10115 Berlin, Germany; [email protected] * Correspondence: [email protected] Abstract: Agates in Paleocene/Eocene tuffs from El Picado/Los Indios, Cuba were investigated to characterize the mineral composition of the agates and to provide data for the reconstruction of agate forming processes. The volcanic host rocks are strongly altered and fractured and contain numerous fissures and veins mineralized by quartz and chalcedony. These features indicate secondary alteration and silicification processes during tectonic activities that may have also resulted in the formation of massive agates. Local accumulation of manganese oxides/hydroxides, as well as uranium (uranyl-silicate complexes), in the agates confirm their contemporaneous supply with SiO2 and the origin of the silica-bearing solutions from the alteration processes. The mineral composition Citation: Götze, J.; Stanek, K.; of the agates is characterized by abnormal high bulk contents of opal-CT (>6 wt%) and moganite Orozco, G.; Liesegang, M.; (>16 wt%) besides alpha-quartz. The presence of these elevated amounts of “immature” silica phases Mohr-Westheide, T. Occurrence and Distribution of Moganite and emphasize that agate formation runs through several structural states of SiO2 with amorphous Opal-CT in Agates from silica as the first solid phase. A remarkable feature of the agates is a heterogeneous distribution of Paleocene/Eocene Tuffs, El Picado moganite within the silica matrix revealed by micro-Raman mapping. The intensity ratio of the main −1 (Cuba). Minerals 2021, 11, 531. symmetric stretching-bending vibrations (A1 modes) of alpha-quartz at 465 cm and moganite https://doi.org/10.3390/min11050531 at 502 cm−1, respectively, was used to depict the abundance of moganite in the silica matrix. The zoned distribution of moganite and variations in the microtexture and porosity of the agates indicate Academic Editor: Galina Palyanova a multi-phase deposition of SiO2 under varying physico-chemical conditions and a discontinuous silica supply. Received: 27 April 2021 Accepted: 12 May 2021 Keywords: agate; alpha-quartz; chalcedony; moganite; opal-CT; Raman spectroscopy Published: 18 May 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in 1. Introduction published maps and institutional affil- iations. Cuba is a country that is particularly famous for its enormous deposits of Ni ores. Huge surficial laterite horizons in the eastern part of the Caribbean island belong to the most important nickel deposits in the world and contain considerable amounts of other valuable chemical compounds of, e.g., Sc, Co, or rare earth elements (REE) [1]. However, occurrences of other mineral deposits are rare and restricted to a few locations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. For instance, different gemstones were exploited between 1989 and 1998 in Cuba, This article is an open access article especially silica minerals and rocks such as chalcedony, opal, jasper or silicites [2]. Remark- distributed under the terms and able are chalcedony from Palmira near Cienfuegos, opal from Loma de los Ópalos and conditions of the Creative Commons Pontezuela (near Camagüey) as well as silicites from Corralillo on the northern coast of Attribution (CC BY) license (https:// Cuba (Figure1). Silicified wood occurs in Upper Cretaceous volcanic sequences of the creativecommons.org/licenses/by/ Sierra de Najasa SE of Camagüey (Sibanicu) and above ophiolites in the Sierra de Cubitas 4.0/). north of Camagüey (Miocene) [2,3]. Minerals 2021, 11, 531. https://doi.org/10.3390/min11050531 https://www.mdpi.com/journal/minerals Minerals 2021, 11, 531 2 of 13 Minerals 2021, 11, x FOR PEER REVIEW 2 of 13 Figure 1. A geomorphological map of Cuba showing occurrences of different SiO2 mineralization. Figure 1. A geomorphological map of Cuba showing occurrences of different SiO2 mineralization. Agates were sporadically found in Upper Cretaceous rocks overlaying ophiolites of Agates were sporadically found in Upper Cretaceous rocks overlaying ophiolites of the Camagüey fault zone NE of Camagüey. In addition, chalcedony, jasper and silicified the Camagüey fault zone NE of Camagüey. In addition, chalcedony, jasper and silicified corals are reported from the Rio Yumuri region near Matanzas [2]. In the eastern part of corals are reported from the Rio Yumuri region near Matanzas [2]. In the eastern part of Cuba, silica mineralization occurs in particular in the surrounding area of Moa. Jasper was Cuba,found silica in altered mineralization serpentinites occurs of the inCosta particular de Moa in region, the surrounding whereas agates/chalcedony area of Moa. Jasperoc- wascurfound in altered in altered volcanic serpentinites rocks in the of region the Costa of El dePicado, Moa W region, of Moa whereas as well agates/chalcedony as near Baracoa occuron the in river altered Toa, volcanic E of Moa rocks (Figure in 1). the region of El Picado, western Moa as well as near BaracoaBecause on the of river the lack Toa, of eastern mineralogical Moa (Figure data,1 ).the agates of the Moa region were in the focusBecause of the present of the lack study. of mineralogicalMineralogical and data, geochemical the agates investigations of the Moa region were wereaimed in to the focuscharacterize of the present the silica study. minerals Mineralogical in the agates and and geochemical to provide data investigations for the reconstruction were aimed of to characterizeagate formation the silicaprocesses minerals in Moa. in On the the agates other and hand, to the provide results data of the for study the reconstruction should pro- ofvide agate additional formation general processes arguments in Moa. for Onthe theongoing other discussion hand, the concerning results of the the study enigma should of provideagate genesis additional [3,4]. generalEmphasis arguments was placed for on the the ongoing detection discussion and distribution concerning of the the mono- enigma ofclinic agate silica genesis polymorph [3,4]. moganite Emphasis and was opal-CT, placed which on the both detection occur in andconsiderable distribution amounts of the monoclinicin the agates silica from polymorph the surroundings moganite of Moa. and opal-CT, which both occur in considerable amounts in the agates from the surroundings of Moa. 2. Geological Background and Sample Material 2. GeologicalThe geology Background of Cuba is and dominated Sample by Material metamorphic and sedimentary rocks. The ge- ographicThe geology position ofin Cubaa tectonically is dominated active byregion, metamorphic with plate andmovements sedimentary in Mesozoic rocks. to The geographicCenozoic times position along in NE a tectonically trending fault active systems, region, resulted with platein a geologic movements trisection in Mesozoic [5]. The to Cenozoicwestern part times of alongthe island NE is trending mainly characterized fault systems, by resulted carbonate in asediments geologic and trisection widespread [5]. The westernkarst formation. part of the The island central is mainly part (Escambray) characterized consists by carbonate of ophiolites, sediments lifted andmetamorphic widespread karstrocks formation. and carbonate The sediments. central part The (Escambray) eastern part consistsof Cuba ofis dominated ophiolites, by lifted the largest metamorphic oph- rocksiolite andcomplexes carbonate of the sediments. Caribbean, TheK-poor eastern volcanic part rocks of Cuba (and isassociated dominated intrusive by the rocks) largest ophioliteof the Paleogene complexes to Eocene of the Caribbean,island arc volcanism, K-poor volcanic as well rocksas overlaying (and associated calcareous intrusive sedi- rocks)ments of [5]. the Paleogene to Eocene island arc volcanism, as well as overlaying calcareous sedimentsThe investigated [5]. agate material derives from El Picado near the village of Los Indios, ca. 15The km investigated west of the agate city of material Moa (Figure derives 1). from The Elhost Picado rocks nearare strongly the village altered of Los Paleo- Indios, ca.cene/Eocene 15 km west tuffs of the(ca. city55 Ma) of Moalocally (Figure intercal1).ated The with host limestones. rocks are stronglyThe altered altered volcanic Pale- ocene/Eocenerocks are fractured tuffs (ca.and 55contain Ma) locallynumerous intercalated fissures and with veins limestones. mineralized The by altered quartz volcanic and rockschalcedony, are fractured indicating and a contain secondary numerous silicification fissures of the and pyroclastic veins mineralized material during by quartz tectonic and chalcedony,activities (Figure indicating 2). a secondary silicification of the pyroclastic material during tectonic activitiesXRD (Figure studies2). of
Recommended publications
  • Download PDF About Minerals Sorted by Mineral Name
    MINERALS SORTED BY NAME Here is an alphabetical list of minerals discussed on this site. More information on and photographs of these minerals in Kentucky is available in the book “Rocks and Minerals of Kentucky” (Anderson, 1994). APATITE Crystal system: hexagonal. Fracture: conchoidal. Color: red, brown, white. Hardness: 5.0. Luster: opaque or semitransparent. Specific gravity: 3.1. Apatite, also called cellophane, occurs in peridotites in eastern and western Kentucky. A microcrystalline variety of collophane found in northern Woodford County is dark reddish brown, porous, and occurs in phosphatic beds, lenses, and nodules in the Tanglewood Member of the Lexington Limestone. Some fossils in the Tanglewood Member are coated with phosphate. Beds are generally very thin, but occasionally several feet thick. The Woodford County phosphate beds were mined during the early 1900s near Wallace, Ky. BARITE Crystal system: orthorhombic. Cleavage: often in groups of platy or tabular crystals. Color: usually white, but may be light shades of blue, brown, yellow, or red. Hardness: 3.0 to 3.5. Streak: white. Luster: vitreous to pearly. Specific gravity: 4.5. Tenacity: brittle. Uses: in heavy muds in oil-well drilling, to increase brilliance in the glass-making industry, as filler for paper, cosmetics, textiles, linoleum, rubber goods, paints. Barite generally occurs in a white massive variety (often appearing earthy when weathered), although some clear to bluish, bladed barite crystals have been observed in several vein deposits in central Kentucky, and commonly occurs as a solid solution series with celestite where barium and strontium can substitute for each other. Various nodular zones have been observed in Silurian–Devonian rocks in east-central Kentucky.
    [Show full text]
  • Understanding the Art of Quartz
    AIA & IDCEC Continuing Education Program UNDERSTANDING THE ART OF QUARTZ PRESENTED BY: AND 1 Hanwha L&C | Surfaces is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES) and Interior Designers Continuing Education Council (IDCEC). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members or to IDCEC for IIDA, ASID or IDC members. Certificates of Completion for both members and non- members are available upon request. This program is registered with AIA/CES and IDCEC for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA or the IDCEC of any material of construction or any method or manner of handling, using, distributing or dealing in any material or product. Questions related to specific materials, methods and services will be addressed at the conclusion of this presentation. This presentation is protected by US and International copyrights laws. Reproduction, distribu- tion, display and use of the presentation without written permission of the speaker is prohibited. Hanwha L&C | Surfaces 2016. 2 AIA & IDCEC Continuing Education Program ∆ Format: Presented f2f in real-time ∆ Course Credit: ◊ AIA: 1 Learning Unit (LU) ◊ Course #: 004QS ◊ IDCEC: .1 Health & Safety ◊ Course #: 40276 ◊ RAIC: 1 Self-Reporting Hour Δ Completion Certificate: ◊ A copy will be provided to you by email, fax, or mail upon request. 3 Learning Objectives ∆ Gain knowledge about natural quartz surfacing: ◊ Composition and Uses ◊ Product Characteristics ◊ Manufacturing and Fabrication ◊ Application and Design Options 4 INTRODUCTION TO QUARTZ Quartz Facts ∆ Quartz is the 4th hardest crystalline mineral on Earth, and it is found abundantly all over the world in a variety of forms.
    [Show full text]
  • Rhodochrosite Gems Unstable Colouration of Padparadscha-Like
    Volume 36 / No. 4 / 2018 Effect of Blue Fluorescence on the Colour Appearance of Diamonds Rhodochrosite Gems The Hope Diamond Unstable Colouration of in London Padparadscha-like Sapphires Volume 36 / No. 4 / 2018 Cover photo: Rhodochrosite is prized as both mineral specimens and faceted stones, which are represented here by ‘The Snail’ (5.5 × 8.6 cm, COLUMNS from N’Chwaning, South Africa) and a 40.14 ct square-cut gemstone from the Sweet Home mine, Colorado, USA. For more on rhodochrosite, see What’s New 275 the article on pp. 332–345 of this issue. Specimens courtesy of Bill Larson J-Smart | SciAps Handheld (Pala International/The Collector, Fallbrook, California, USA); photo by LIBS Unit | SYNTHdetect XL | Ben DeCamp. Bursztynisko, The Amber Magazine | CIBJO 2018 Special Reports | De Beers Diamond ARTICLES Insight Report 2018 | Diamonds — Source to Use 2018 The Effect of Blue Fluorescence on the Colour 298 Proceedings | Gem Testing Appearance of Round-Brilliant-Cut Diamonds Laboratory (Jaipur, India) By Marleen Bouman, Ans Anthonis, John Chapman, Newsletter | IMA List of Gem Stefan Smans and Katrien De Corte Materials Updated | Journal of Jewellery Research | ‘The Curse Out of the Blue: The Hope Diamond in London 316 of the Hope Diamond’ Podcast | By Jack M. Ogden New Diamond Museum in Antwerp Rhodochrosite Gems: Properties and Provenance 332 278 By J. C. (Hanco) Zwaan, Regina Mertz-Kraus, Nathan D. Renfro, Shane F. McClure and Brendan M. Laurs Unstable Colouration of Padparadscha-like Sapphires 346 By Michael S. Krzemnicki, Alexander Klumb and Judith Braun 323 333 © DIVA, Antwerp Home of Diamonds Gem Notes 280 W.
    [Show full text]
  • Tiger's Eye Is Not a Pseudomorph Glenn Morita in the Early 1800’S, Mineralogists Recognized That Tiger’S Eye Was a Fibrous Variey of Quartz
    Minutes of the 05/20/03 Westside Board Meeting VP Stu Earnst opened the meeting at 7:31pm. Treasurer’s report read by Kathy Earnst. Minutes approved as published in the newsletter. Old business: Lease on Walker valley discussed. The expiration notice was sent but we are not sure who it went to. We do not see any obstacle to renewal as communication between the council and DNR are open and ongoing. Special thanks, to DNR representative, Laurie Bergvall and DNR staff for their time and effort in hearing our concerns and working towards mutually beneficial solutions on the Walker Valley issues. Sign production is on hold until the sign committee decides where and what the signs will say. We have decided that they will not be on the gate but separate from it. There will be a gate going up at Walker Valley but we will have access to that lock and it will probably be a combo type of thing that we can easily give to other rockhound clubs going there. Talked about the possibility of posing the combo on website but that will depend on the type of gate they put up and what ends up being possible with the mechanics of that gate. New business: Thank you from Bob Pattie and Ed Lehman to Bruce Himko and AAA Printing for donation of the paper. Thank you to Danny Vandenberg for providing sample Walker Valley Material to DNR to show the value of the material we are trying to preserve and enjoy. Bob Pattie is pursuing with the retrieval of our state seized funds through the unclaimed property process.
    [Show full text]
  • City of St. Peters Board of Aldermen Tentative Agenda for Regular Meeting St
    CITY OF ST. PETERS BOARD OF ALDERMEN TENTATIVE AGENDA FOR REGULAR MEETING ST. PETERS JUSTICE CENTER, 1020 GRAND TETON DRIVE, ST. PETERS, MO 63376 OCTOBER 22, 2020 – 6:30 P.M. A. Call to Order, Mayor Len Pagano B. Roll Call C. Opening Ceremonies 1. Invocation 2. Pledge of Allegiance 3. Proclamations: National Arts and Humanities Month, Jill Tutt 4. Presentation: No Hunger Holiday, Mike Narkawicz 5. Recognition: Random Acts of Kindness D. Approval of Minutes: The Board of Aldermen Work Session meeting of October 8, 2020; and the Regular Board of Aldermen meeting of October 8, 2020. E. Reports of Officers, Boards and Commissions 1. Mayoral Report of Appointments to Boards and Commissions a. Appointment to the Veterans Memorial Commission 2. City Administrator’s Report: 3. Report of Director, Planning, Community and Economic Development: 4. St. Peters Business Spotlight: None F. Open Forum 1. Citizens Petitions and Comments 2. Communications from the Elected Officials 3. Announcements G. Public Hearings: None H. Unfinished Business Items: None I. New Business Items: 1. Bill No. 20-118: Bill authorizing the City Administrator of the City of St. Peters, Missouri, to execute a Certain Subrecipient Agreement between St. Charles County (Grantee) and the City of St. Peters (Subrecipient) for conducting City Community Development Block Grant (CDBG) Programs with 2020 Federal Funding 2. Bill No. 20-119: Bill of the City of St. Peters, Missouri, deleting Chapter 615 of the Code of the City of St. Peters, Missouri, in its entirety; enacting, in lieu thereof, a new Chapter 615; and providing for the licensing and regulation of body art establishments and body artists 3.
    [Show full text]
  • Lapidary Journal Jewelry Artist March 2012
    INDEX TO VOLUME 65 Lapidary Journal Jewelry Artist April 2011-March 2012 INDEX BY FEATURE/ Signature Techniques Part 1 Resin Earrings and Pendant, PROJECT/DEPARTMENT of 2, 20, 09/10-11 30, 08-11 Signature Techniques Part 2 Sagenite Intarsia Pendant, 50, With title, page number, of 2, 18, 11-11 04-11 month, and year published Special Event Sales, 22, 08-11 Silver Clay and Wire Ring, 58, When to Saw Your Rough, 74, 03-12 FEATURE ARTICLES Smokin’*, 43, 09/10-11 01/02-12 Argentium® Tips, 50, 03-12 Spinwheel, 20, 08-11 Arizona Opal, 22, 01/02-12 PROJECTS/DEMOS/FACET Stacking Ring Trio, 74, Basic Files, 36, 11-11 05/06-11 DESIGNS Brachiopod Agate, 26, 04-11 Sterling Safety Pin, 22, 12-11 Alabaster Bowls, 54, 07-11 Create Your Best Workspace, Swirl Step Cut Revisited, 72, Amethyst Crystal Cross, 34, 28, 11-11 01/02-12 Cut Together, 66, 01/02-12 12-11 Tabbed Fossil Coral Pendant, Deciphering Chinese Writing Copper and Silver Clay 50, 01/02-12 Linked Bracelet, 48, 07-11 12, 07-11 Stone, 78, 01/02-12 Torch Fired Enamel Medallion Site of Your Own, A, 12, 03-12 Easier Torchwork, 43, 11-11 Copper Wire Cuff with Silver Necklace, 33, 09/10-11 Elizabeth Taylor’s Legendary Wire “Inlay,” 28, 07-11 Trillion Diamonds Barion, 44, SMOKIN’ STONES Jewels, 58, 12-11 Coquina Pendant, 44, 05/06-11 Alabaster, 52, 07-11 Ethiopian Opal, 28, 01/02-12 01/02-12 Turquoise and Pierced Silver Ametrine, 44, 09/10-11 Find the Right Findings, 46, Corrugated Copper Pendant, Bead Bracelet – Plus!, 44, Coquina, 42, 01/02-12 09/10-11 24, 05/06-11 04-11 Fossilized Ivory, 24, 04-11
    [Show full text]
  • March 2019 Agate Explorer.Pub
    Cuyuna Rock, Gem and Mineral Society The Agate Explorer March 2019 Summer Field Trip Plans are being made for a long weekend trip to Thunder Bay to collect amethyst. The tentative dates are Friday -Sunday, July 5 -7. A sign -up sheet will be available at upcoming meeting in order to plan this trip. It is necessary to have a passport to travel to Canada. You may also check to see if an enhanced driver’s license is acceptable. March meeting Open Shop from 9 a.m. —noon Franklin Art Center Club member, Ray Strassberg, will be available for members to learn how Club Information to cut rocks using the 10” or 16” inch saws. Website -www.cuyunarockclub.org - Email [email protected] Bring rocks of your own or purchase something in the Rock Room. Meeting Place Lower level Franklin Arts Center Kids’ Program 1001 Kingwood St, Brainerd, MN 56401 Did you know that there are many Directions .4 mile east of Business Hwy. 371 different kinds of Lake Superior & Hwy. 210 intersection. agates? Lisa will tell you all about it (Castle turret water tower.) at the March meeting! Date/Time the 2nd Saturday of each month Rock Wrappers at 2 p.m. unless otherwise noted. Meets starting at 10 a.m. on meeting Saturdays. Club Dues $20/ family ,An open gathering for wire wrappers. Hang out with other wrappers, Free /unaccompanied juniors and work on your projects. (Bring all supplies needed.) Membership runs Learn tricks to make wrapping easier, a new design, from Jan. 1-Dec. 31st. or perhaps a new place to find supplies.
    [Show full text]
  • Fall 2015 Gems & Gemology
    FALL 2015 VOLUME LI THE UARTERLY JOURNAL OF THE GEMOLOGICAL INSTITUTE OF AMERICA Colombian Trapiche Emeralds Large Colorless HPHT-Grown Synthetic Diamonds Diamonds from the Letšeng Mine Fall 2015 VOLUME 51, No. 3 EDITORIAL 221 Trapiche and More... Duncan Pay FEATURE ARTICLES 222 Colombian Trapiche Emeralds: Recent Advances in Understanding Their Formation Isabella Pignatelli, Gaston Giuliani, Daniel Ohnenstetter, Giovanna Agrosì, pg. 254 Sandrine Mathieu, Christophe Morlot, and Yannick Branquet Proposes a model for trapiche emerald formation based on petrographic, spectroscopic, and chemical examination. 260 Large Colorless HPHT-Grown Synthetic Gem Diamonds from New Diamond Technology, Russia Ulrika F.S. D’Haenens-Johansson, Andrey Katrusha, Kyaw Soe Moe, Paul Johnson, and Wuyi Wang pg. 270 Examines a new source of colorless and near-colorless gem-quality HPHT synthetic diamonds using spectroscopic and gemological analysis. 280 Letšeng’s Unique Diamond Proposition Russell Shor, Robert Weldon, A.J.A. (Bram) Janse, Christopher M. Breeding, and Steven B. Shirey Explores the history, geology, and current production of this unique source of large diamonds. NOTES AND NEW TECHNIQUES 300 Origin Determination of Dolomite-Related White Nephrite through Iterative-Binary Linear Discriminant Analysis Zemin Luo, Mingxing Yang, and Andy H Shen A technique for origin identification based on statistical analysis and LA-ICP-MS spectrometry. pg. 293 REGULAR FEATURES 312 Lab Notes Unusual graining structure in pink diamond • Yellow HPHT-treated rough diamond
    [Show full text]
  • Symposium on Agate and Cryptocrystalline Quartz
    Symposium on Agate and Cryptocrystalline Quartz September 10 – 13, 2005 Golden, Colorado Sponsored by Friends of Mineralogy, Colorado Chapter; Colorado School of Mines Geology Museum; and U.S. Geological Survey 2 Cover Photos {top left} Fortification agate, Hinsdale County, Colorado, collection of the Geology Museum, Colorado School of Mines. Coloration of alternating concentric bands is due to infiltration of Fe with groundwater into the porous chalcedony layers, leaving the impermeable chalcedony bands uncolored (white): ground water was introduced via the symmetric fractures, evidenced by darker brown hues along the orthogonal lines. Specimen about 4 inches across; photo Dan Kile. {lower left} Photomicrograph showing, in crossed-polarized light, a rhyolite thunder egg shell (lower left) a fibrous phase of silica, opal-CTLS (appearing as a layer of tan fibers bordering the rhyolite cavity wall), and spherulitic and radiating fibrous forms of chalcedony. Field of view approximately 4.8 mm high; photo Dan Kile. {center right} Photomicrograph of the same field of view, but with a 1 λ (first-order red) waveplate inserted to illustrate the length-fast nature of the chalcedony (yellow-orange) and the length-slow character of the opal CTLS (blue). Field of view about 4.8 mm high; photo Dan Kile. Copyright of articles and photographs is retained by authors and Friends of Mineralogy, Colorado Chapter; reproduction by electronic or other means without permission is prohibited 3 Symposium on Agate and Cryptocrystalline Quartz Program and Abstracts September 10 – 13, 2005 Editors Daniel Kile Thomas Michalski Peter Modreski Held at Green Center, Colorado School of Mines Golden, Colorado Sponsored by Friends of Mineralogy, Colorado Chapter Colorado School of Mines Geology Museum U.S.
    [Show full text]
  • Get Reactive in System 96!
    Get Reactive in System 96! Uroboros has created two unique glass formulas for System 96 that are designed to create an interface color, or a reac on, when melted against certain other colors. This occurs when ions from the two adjacent glasses migrate and mingle when the gl asses become hot and ß uid. Given the right glass chemistry, the comingled ions form a very thin colored line, or reac on. Since our formulas react to create a no ceably reddish hue we named them Red Reac ves: as in Red Reac ve Transparent, and Red Reac ve Opal. The primary ingredient needed in a glass to generate a reac on color with our Reac ve glass is Copper. Copper is present in many blue and blue-green glass colors, but in some cases in too low a concentra on to create a no ceable reac on. For simplicity, all System 96 colors have been graded for their poten al to react into three categories: Strong, Medium, and Mild. See them all listed in the chart on the back of this page. You will Þ nd that the intensity of the reac on color will get stronger with longer, ho er, or repeat Þ rings. This is because the copper ions have more me to mingle with their friendly reac ve partners in the adjacent glass. The chart rankings are based on a typical single Þ ring cycle. You could get a Medium reac on from a color graded as Mild by Þ ring it ho er, or Þ ring mul ple mes.
    [Show full text]
  • AMETHYSTINE CHALCEDONY by James E
    NOTES ANDa NEW TECHNIQUES AMETHYSTINE CHALCEDONY By James E. Shigley and John I. Koivula A new amethystine chalcedony has been discovered in that this is one of the few reported occurrences Arizona. The material, marketed under the trade name where an amethyst-like, or amethystine, chalced- "Damsonite," is excellent for both jewelry and carv- ony has been found in quantities of gemological ings. The authors describe thegemological properties of importance (see Frondel, 1962). Popular gem this new type of chalcedony, and report the effects of hunters' guides, such as MacFall (1975) and heat treatment on it. Although this purple material is Anthony et al. (19821, describe minor occurrences apparently b.new color type of chalcedony, it has the same gemological properties as the other better-known in Arizona of banded purple agate, but give no types. It corresponds to a microcrystalline form of ame- indication of deposits of massive purple chalced- thyst which, when heat treated at approximately ony similar to that described here. This article 500°C becomes yellowish orange, as does some briefly summarizes the occurrence, gemological single-crystal amethyst. properties, and reaction to heat treatment of this material. LOCALITY AND OCCURRENCE The purple chalcedony described here has been Chalcedony is a microcrystalline form of quartz found at a single undisclosed locality in central that occurs in a wide variety of patterns and colors. Arizona. It was first noted as detrital fragments in Numerous types of chalcedony, such as chryso- the bed of a dry wash that cuts through a series of prase, onyx, carnelian, agate, and others, have been sedimentary rocks.
    [Show full text]
  • Origin of Fibrosity and Banding in Agates from Flood Basalts: American Journal of Science, V
    Agates: a literature review and Electron Backscatter Diffraction study of Lake Superior agates Timothy J. Beaster Senior Integrative Exercise March 9, 2005 Submitted in partial fulfillment of the requirements for a Bachelor of Arts degree from Carleton College, Northfield, Minnesota. 2 Table of Contents AGATES: A LITERATURE REVEW………………………………………...……..3 Introduction………………....………………………………………………….4 Structural and compositional description of agates………………..………..6 Some problems concerning agate genesis………………………..…………..11 Silica Sources…………………………………………..………………11 Method of Deposition………………………………………………….13 Temperature of Formation…………………………………………….16 Age of Agates…………………………………………………………..17 LAKE SUPERIOR AGATES: AN ELECTRON BACKSCATTER DIFFRACTION (EBSD) ANALYSIS …………………………………………………………………..19 Abstract………………………………………………………………………...19 Introduction……………………………………………………………………19 Geologic setting………………………………………………………………...20 Methods……………………………………………………...…………………20 Results………………………………………………………….………………22 Discussion………………………………………………………………………26 Conclusions………………………………………………….…………………26 Acknowledgments……………………………………………………..………………28 References………………………………………………………………..……………28 3 Agates: a literature review and Electron Backscatter Diffraction study of Lake Superior agates Timothy J. Beaster Carleton College Senior Integrative Exercise March 9, 2005 Advisor: Cam Davidson 4 AGATES: A LITERATURE REVEW Introduction Agates, valued as semiprecious gemstones for their colorful, intricate banding, (Fig.1) are microcrystalline quartz nodules found in veins and cavities
    [Show full text]