Baking black opal in the desert sun: The importance of silica in desert varnish

Abstract

Research Article| July 01, 2006 Baking black opal in the desert sun: The importance of silica in desert varnish Randall S. Perry; Randall S. Perry 1Impacts and Astromaterials Research Centre, Department of Earth Science and Engineering, South Kensington Campus, Imperial College, London SW7 2AZ, UK, and Planetary Science Institute, Seattle, Washington 98115, USA Search for other works by this author on: GSW Google Scholar Bridget Y. Lynne; Bridget Y. Lynne 2Department of Geology, University of Auckland, Private Bag 92019, Auckland, New Zealand Search for other works by this author on: GSW Google Scholar Mark A. Sephton; Mark A. Sephton 3Impacts and Astromaterials Research Centre, Department of Earth Science and Engineering, South Kensington Campus, Imperial College, London SW7 2AZ, UK Search for other works by this author on: GSW Google Scholar Vera M. Kolb; Vera M. Kolb 4Department of Chemistry, University of Wisconsin-Parkside, Kenosha, Wisconsin 53141-2000, USA Search for other works by this author on: GSW Google Scholar Carole C. Perry; Carole C. Perry 5Chemistry Division, School of Biomedical Natural Sciences, Nottingham Trent University, Clifton Lane, Nottingham NG118NS, UK Search for other works by this author on: GSW Google Scholar James T. Staley James T. Staley 6Department of Microbiology, School of Medicine, University of Washington, Seattle, Washington 98195-1310, USA Search for other works by this author on: GSW Google Scholar Geology (2006) 34 (7): 537–540. https://doi.org/10.1130/G22352.1 Article history received: 07 Nov 2005 rev-recd: 08 Feb 2006 accepted: 12 Feb 2006 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Randall S. Perry, Bridget Y. Lynne, Mark A. Sephton, Vera M. Kolb, Carole C. Perry, James T. Staley; Baking black opal in the desert sun: The importance of silica in desert varnish. Geology 2006;; 34 (7): 537–540. doi: https://doi.org/10.1130/G22352.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Desert varnish, a widespread black manganese-rich rock coating, contains labile organic compounds, but a mechanism for its formation and for their preservation remains unproven. Using Raman spectroscopy, X-ray diffraction, and scanning transmission electron microscopy, we analyzed varnish and found amorphous hydrated silica (opal) and the silica mineral moganite, similar to findings we have reported from siliceous hot-spring deposits. We suggest that the slow dissolution of silica from anhydrous and hydrous minerals, and its subsequent gelling, condensation, and hardening, provides a simple explanation of a formation mechanism for desert varnish and silica glazes and the incorporation of organic material from local environments. These chemical signatures, sequestered in silica, provide valuable information about terrestrial and extraterrestrial paleoenvironments. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.