Characterisation and Genesis of Sapphires from the Yenya-U Area, Thabeikkyin Township, Mandalay Region, Myanmar

• Published in: Journal of gemmology (1986) Vol. 37; no. 8; pp. 802 - 815
• Main Authors: Phyu, Khin Mar, Zaw, Khin, Mernagh, Terrence Patrick, Aung, Thu Zar
• Format: Journal Article
• Language: English
• Published: London Gem-A, The Gemmological Association of Great Britain 01.01.2021; The Gemmological Association of Great Britain
• Subjects: Age; Distribution; Gemology; Identification and classification; Isotopes; Marble; Paleocene; Properties; Sapphires; Myanmar; Myanmar (Burma)
• ISSN: 1355-4565; 2632-1718
• DOI: 10.15506/JoG.2021.37.8.802

The Yenya-U area in the Mandalay region of central Myanmar hosts two primary sapphire deposits, at Kyauk-tagar and Kyar-gaung. The sapphires form disseminated crystals within syenite pegmatite and nepheline syenite, respectively. Kyar-gaung is a source of relatively large crystals (up to 12 g) that are translucent to opaque, while Kyauk-tagar produces fine-quality vivid-blue sapphires in smaller sizes (up to 0.4 g). Alluvial deposits in the region yield high-quality sapphires of various colours (including colourless, yellow, purple, pink, greenish blue and blue), as well as quartz, topaz, spinel, garnet, zircon, tourmaline and fluorite. The studied Yenya-U sapphires contained solid inclusions of albite, biotite, graphite, melanophlogite and diaspore. In addition, pennantite is reported here for the first time as an inclusion in corundum. C[O.sub.2]-rich fluid inclusions were commonly observed in most of the sapphires. Trace-element analyses of the sapphires are consistent with a metamorphic-metasomatic origin, mostly accompanied by desilicification processes.