Gem corundum deposits in Vietnam

Van Long, P., Quang Vinh, H., Garnier, V., Giuliani, G., Ohnenstetter, D., Lhomme, T., Schwarz, D., Fallick, A.E., Dubessy, J. and Trong Trinh, P. (2004) Gem corundum deposits in Vietnam. Journal of Gemmology, 29(3), pp. 129-147.

Abstract

Since 1983, gem-quality rubies have been recovered from the Luc Yen and Quy Chau mining areas in northern Vietnam. Since 1991, 'basaltic'-type blue-green-yellow ('BGY') sapphires have been mined in southern Vietnam. This article briefly reviews the history and geology of these different areas and shows the importance of marble and basalt-type deposits. Other types of corundum occurrences are found in amphibolite, pegmatite, gneiss and metasomatite. The gemmological, chemical and isotopic characteristics of these different types of corundum are described.<br /> The most notable features of rubies contained in marbles are that many crystals have blue colour zones, and inclusions of rutile, anhydrite and salts. The primary fluid inclusions are composed of carbon dioxide and hydrogen sulphide with native sulphur and diaspore daughter minerals. Sapphires from placers in basalts are characterized by inclusions of columbite, pyrochlore and baddeleyite. The trace element contents of corundums allow distinction of rubies in marbles from sapphires in basalts and metamorphic rocks. Rubies have high chromium (0.54<Cr₂O₃<O.66 wt.%)and low iron (0.01<FeO<0.07 wt.%) contents. The geological origin of Vietnam corundums can be clearly determined from the isotopic composition of their structural oxygen, i.e. δ 18O = 21.0 ± 0.9% for rubies in marbles and δ 18O = 6.6 ± 0.4% for sapphires in basalts.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Fallick, Professor Anthony
• Authors: Van Long, P., Quang Vinh, H., Garnier, V., Giuliani, G., Ohnenstetter, D., Lhomme, T., Schwarz, D., Fallick, A.E., Dubessy, J., and Trong Trinh, P.
• Subjects: Q Science > QE Geology
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Journal of Gemmology
• Publisher: Gemmological Association and Gem Testing Laboratory of Great Britain
• ISSN: 1355-4565
• Copyright Holders: ©Gemmological Association and Gem Testing Laboratory of Great Britain
• First Published: First published in the Journal of Gemmology29(2):129-147
• Publisher Policy: Reproduced with the permission of the Publisher