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Johnkoivulaite, Cs(Be₂B)Mg₂Si₆O₁₈, a new mineral of the beryl group from the gem deposits of Mogok, Myanmar

Palke, Aaron C. and Henling, Lawrence M. and Ma, Chi and Rossman, George R. and Sun, Ziyin and Renfro, Nathan and Kampf, Anthony R. and Thu, Kyaw and Myo, Nay and Wongrawang, Patcharee and Weeramonkhonlert, Vararut (2021) Johnkoivulaite, Cs(Be₂B)Mg₂Si₆O₁₈, a new mineral of the beryl group from the gem deposits of Mogok, Myanmar. American Mineralogist, 106 (11). pp. 1844-1851. ISSN 0003-004X. doi:10.2138/am-2021-7785. https://resolver.caltech.edu/CaltechAUTHORS:20211116-175049061

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Abstract

A new mineral of the beryl group, johnkoivulaite, Cs(Be₂B)Mg₂Si₆O₁₈, was recovered from the gem gravels in the Pein Pyit area of the Mogok region in Myanmar. Thus far, only a single crystal has been identified. It has dimensions of about 5.8 × 5.7 × 5.5 mm. This specimen has an irregular shape but still has discernible crystal form with geometric growth patterns observed on the crystal faces. The crystal of johnkoivulaite is grayish-violet in color and strongly pleochroic, going from nearly colorless with E┴c to dark bluish-violet with E||c. Johnkoivulaite has a Mohs hardness of about 7½ and a measured density of 3.01(10) g/cm³. It is uniaxial (–) with ω = 1.607(1) and ε = 1.605(1) (white light). Electron microprobe analyses gave the empirical formula of (Cs_(0.85)K_(0.10)Na_(0.01))(Be_(1.88)B_(1.12))(Mg_(1.66)Fe_(0.27)Mn_(0.01)Al_(0.05)) (Si_(5.98))O₁₈ with Be calculated by stoichiometry and confirmed by LA-ICP-MS measurements. Johnkoivulaite is hexagonal, P6/mmc (no. 192) with a = 9.469(2), c = 9.033(2) Å, V = 701.5(3) ų, and Z = 2. Johnkoivulaite is isostructural with beryl and exhibits partial substitution of B for Be at the distorted tetrahedral site, Mg for Al at the octahedral site, and Cs in the channel sites within the stacked Si₆O₁₈ rings. This substitution can be written as (CsMg₂B)(☐Al₂Be)₋₁. Johnkoivulaite, the seventh member of the beryl group, is named in honor of gemologist John Koivula in recognition of his contributions to mineralogy and gemology.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.2138/am-2021-7785DOIArticle
http://www.minsocam.org/MSA/AmMin/TOC/2021/Nov2021_data/AM-21-117785.zipPublisherSupporting Information
ORCID:
AuthorORCID
Palke, Aaron C.0000-0001-5467-6119
Ma, Chi0000-0002-1828-7033
Rossman, George R.0000-0002-4571-6884
Kampf, Anthony R.0000-0001-8084-2563
Alternate Title:Johnkoivulaite, Cs(Be2B)Mg2Si6O18, a new mineral of the beryl group from the gem deposits of Mogok, Myanmar
Additional Information:© 2021 Mineralogical Society of America. Manuscript received September 1, 2020; Manuscript accepted November 25, 2020; Manuscript handled by Fabrizio Nestola. We thank two reviewers for their constructive comments and suggestions that have strengthened this manuscript. We also thank Mike Breeding (GIA) and Evan Smith (GIA) for reading the manuscript and providing additional comments and editing for grammar and style. Much gratitude is owed to Associate Editor Fabrizio Nestola and the rest of the editorial staff at American Mineralogist as well. The Bruker D8 Kappa X-ray diffractometer was purchased via an NSF CRIF:MU award to the California Institute of Technology (CHE-0639094) and upgraded with a Dow Next Generation Instrumentation Grant. EPMA analysis was carried out at the Caltech GPS Division Analytical Facility, which is supported, in part, by NSF Grants EAR-0318518 and DMR-0080065. George Rossman’s contribution to this work was also supported by NSF Grant EAR-1322082. A portion of this study was funded by the John Jago Trelawney Endowment to the Mineral Sciences Department of the Natural History Museum of Los Angeles County. Deposit item AM-21-117785, Online Materials. Deposit items are free to all readers and found on the MSA website, via the specific issue’s Table of Contents (go to http://www.minsocam.org/MSA/AmMin/TOC/2021/Nov2021_data/Nov2021_data.html). The CIF has been peer reviewed by our Technical Editors.
Funders:
Funding AgencyGrant Number
NSFCHE-0639094
Dow Next Generation Educator FundUNSPECIFIED
NSFEAR-0318518
NSFDMR-0080065
NSFEAR-1322082
John Jago Trelawney EndowmentUNSPECIFIED
Subject Keywords:Beryl group, new mineral, gemology, johnkoivulaite, Mogok, Myanmar
Issue or Number:11
DOI:10.2138/am-2021-7785
Record Number:CaltechAUTHORS:20211116-175049061
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20211116-175049061
Official Citation:Aaron C. Palke, Lawrence M. Henling, Chi Ma, George R. Rossman, Ziyin Sun, Nathan Renfro, Anthony R. Kampf, Kyaw Thu, Nay Myo, Patcharee Wongrawang, Vararut Weeramonkhonlert; Johnkoivulaite, Cs(Be2B)Mg2Si6O18, a new mineral of the beryl group from the gem deposits of Mogok, Myanmar. American Mineralogist 2021; 106 (11): 1844–1851. doi: https://doi.org/10.2138/am-2021-7785
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:111896
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:16 Nov 2021 18:27
Last Modified:16 Nov 2021 18:44

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