Fall 2013 Gems & Gemology
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FALL 2013 VOLUME XLIX THE UARTERLY JOURNAL OF THE GEMOLOGICAL INSTITUTE OF AMERICA The Cheapside Hoard: An Extraordinary Collection of Jewels Digit Patterns in Opal Agate from Morocco Field Report on Oregon Sunstone Fall 2013 VOLUME 49, No. 3 EDITORIAL 125 Striving for Timeliness and Synergy Duncan Pay FEATURE ARTICLES 126 The Museum of London’s Extraordinary Cheapside Hoard Robert Weldon and Cathleen Jonathan Reveals the history and mysteries behind a treasure of jewels hidden during the 1600s, a window to the past being fully opened to the public for the first time pg. 129 since a chance discovery a century ago. 138 On the Origin of Digit Patterns in Gem Opal Benjamin Rondeau, Jean-Pierre Gauthier, Francesco Mazzero, Emmanuel Fritsch, Yves Bodeur, and Boris Chauviré Examines this finger-like feature, mostly found in Ethiopian opal, and proposes a multi-step model for its formation. 148 Agates from Sidi Rahal, in the Atlas Mountains of Morocco: Gemological Characteristics and Proposed Origin pg. 143 Magdalena Dum a´nska-Słowik, Lucyna Natkaniec-Nowak, Aleksandra Wesełucha-Bircz y´nska, Adam Gaweł, Marek Lankosz, and Paweł Wróbel Reports on the chemical and mineralogical analysis of solid inclusions in agate from this deposit. NOTES AND NEW TECHNIQUES 160 Useful Visual Clue Indicating Corundum Heat Treatment John I. Koivula pg. 162 Shows the conversion of limonitic residues to hematite in surface-reaching inclusions, a practical indication of heat-treated corundum. FIELD REPORT 162 Three Occurrences of Oregon Sunstone Duncan Pay, Robert Weldon, Shane McClure, and Kevin Schumacher Chronicles a visit to the high desert of eastern Oregon to examine commercial sources of this natural copper-bearing feldspar. REGULAR FEATURES 147 2013 G&G Challenge Winners 172 Lab Notes Imitation rainbow moonstone assemblage • Enormous filled pearl • Diamond with high concentration of nickel • Unusual laser manufacturing remnant • Purple jadeite rock • Determining hydrophane nature of opal • Green sapphire, glass-filled • Large pinkish brown CVD synthetic diamond • Turquoise with fingerprint pattern 178 Gem News International Epigenetic malachite in quartz • Dumbbell-like inclusion in diamond • Boron carbide as black diamond imita - tion • Amber with insect-bearing filling • Phosphorescence in synthetic sapphire • Massive faceted fuchsite • Polymer-coated corundum • Dyed fire opal • June 2013 Hong Kong Jewellery & Gem Fair Editorial Staff Editor-in-Chief Editorial Assistants Duncan Pay Brooke Goedert [email protected] Nathan Renfro gia.edu/gems-gemology Managing Editor Editors, Lab Notes Subscriptions Justin Hunter Thomas M. Moses Copies of the current issue may be purchased for [email protected] Shane F. McClure $29.95 plus shipping. Subscriptions are $79.99 for one year (4 issues) in the U.S. and $99.99 else - Editor Contributing Editors where. Canadian subscribers should add GST. Stuart D. Overlin James E. Shigley Discounts are available for group subscriptions, [email protected] GIA alumni, and current GIA students. For insti - Andy Lucas tutional rates, contact Customer Service. Technical Editors Editor-in-Chief Emeritus To purchase print subscriptions, visit store.gia.edu Tao Z. Hsu Alice S. Keller or contact Customer Service. [email protected] Customer Service Database Coverage Jennifer Stone-Sundberg Martha Erickson Gems & Gemology is abstracted in Thomson Associate Editor (760) 603-4502 Reuters products (Current Contents: Physical, [email protected] Chemical & Earth Sciences and Science Citation Claire Harlin Index— Expanded, including the Web of Knowl - [email protected] edge) and other databases. For a complete list of sources abstracting G&G , go to gia.edu/gems- gemology. 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Washington, DC San Diego, California Carlsbad, California Postmaster: Return undeliverable copies of Gems Alan T. Collins Anthony R. Kampf Christopher P. Smith & Gemology to GIA, The Robert Mouawad London, UK Los Angeles, California New York, New York Campus, 5345 Armada Drive, Carlsbad, CA 92008. John L. Emmett Robert E. Kane Wuyi Wang Our Canadian goods and service registration num - Brush Prairie, Washington Helena, Montana New York, New York ber is 126142892RT. Emmanuel Fritsch Lore Kiefert Christopher M. Welbourn Any opinions expressed in signed articles are un - Nantes, France Lucerne, Switzerland Reading, UK derstood to be opinions of the authors and not of the publisher. Eloïse Gaillou Thomas M. Moses Los Angeles, California New York, New York About the Cover Measuring an estimated 42 mm deep × 20 mm wide, this Colombian emerald pocket watch is one of the most no - table items from the Cheapside Hoard collection, on full display for the first time since its discovery more than 100 years ago. Dating back to the 16th century, the treasure’s nearly 500 antique pieces comprise gems from around the world, each telling a unique story of the time (see article on page 126). Courtesy of the Museum of London; photo by Robert Weldon. Printing is by L+L Printers, Carlsbad, CA. GIA World Headquarters The Robert Mouawad Campus 5345 Armada Drive Carlsbad, CA 92008 USA © 2013 Gemological Institute of America All rights reserved. ISSN 0016-626X STRIVING FOR TIMELINESS AND SYNERGY We hope you enjoy the Fall 2013 Gems & Gemology . For this issue, we present two fascinating papers from European authors, one on Moroccan agate and one on columnar growth patterns in natural opal from Ethiopia. This second paper outlines a persuasive model of forma - tion for the distinctive “digit” patterns characteristic of some gems from this source. We also feature articles from GIA authors on diverse topics ranging from a practical indication of heat treatment to Oregon sunstone to our lead article on the Museum of London’s fabulous Cheapside Hoard. In August, GIA’s Robert Weldon received an invitation to view this astonishing collection, lost for almost 300 years until a chance discovery in 1912 during a demolition near London’s famous St. Paul’s Cathedral. As it was such a rare opportunity—this cache of jewels represents both a tantalizing window into trade patterns of the 1600s and a great story in itself—we accepted the invitation and traveled to the UK to document it. This trip also gave the impetus to produce an The field report, which chronicles a GIA expedition article in time for the Fall 2013 to a gem-producing or processing area and may even G&G , which will coincide with the very first major exhibition of stand as a statement of intent for future lines of re - the jewels. In other words, we had search and publication... an opportunity to be timely and produce what we hope will be the definitive paper on this extraordinary collection. In London, GIA was able to record video interviews with the museum’s staff and a tour of the hoard, which we will make available on our website. In this issue, we’re also introducing a new article category to G&G : the field report, which chronicles a GIA expedition to a gem-producing or processing area and may even stand as a statement of intent for future lines of research and publication. Field reports will also serve as anchors on the GIA website for video and images acquired on these trips. Our first field report documents three sunstone feldspar occurrences in Oregon. Readers will find slideshows plus videos of mining processes and interviews with miners at www.gia.edu/gems-gemology. This rich media allows us to offer a far more comprehensive and engaging picture of a topic than we’ve been able to in the past. This synergy with the GIA website gives us the ability to quickly post articles and news stories online rather than waiting three months for the next print issue. And we can provide supporting resources for our regular print articles that enrich the user experience. We trust we’ve been able to deliver this with the Fall issue and invite you to explore the associated online media for the Cheapside Hoard and Oregon sunstone articles. Let me also take this opportunity to thank all the authors who have submitted manuscripts to G&G for review. We truly value your contributions. Duncan Pay | Editor-in-Chief | [email protected] EDITORIAL GEMS & G EMOLOGY FALL 2013 125 FEATURE ARTICLES THE MUSEUM OF LONDON ’S EXTRAORDINARY CHEAPSIDE HOARD Robert Weldon and Cathleen Jonathan An astonishing collection of jewels, discovered by chance in 1912 after centuries of concealment, is on display at the Museum of London.