By: Lin Sutherland, Category: AMRI, Date: 21 Sep 2018
Study by the AM compared genesis of rubies from two continents at first International Mineralogical Association meeting held in Australia
Trio of notable museum mineralogists at the 2018 International Mineralogical Association meeting, Melbourne
Photographer: Lin Sutherland © Australian Museum
The presentation by Lin Sutherland at the International Mineralogical Association (IMA) Melbourne in August 2018, in the ‘Recent Advances in Our Understanding of Gem minerals’ session, explored genesis of Myanmar and East Australian ruby deposits. Results explained why Myanmar rubies excel over Australian reds.
Several institutions provided field and laboratory results for the synthesis. Personnel with diverse expertise contributed from Geoscience, Australian Museum; Centre of Excellence in Ore Deposit Studies, University of Tasmania, a gem lab at Yangon University, Myanmar, and post-graduate students from University of Mandalay, Myanmar; National University of Malaya, Selengor, and Earth Sciences, University of New South Wales, Sydney.
Rubies analysed from Mong Hsu and Mogok in Myanmar revealed the colour-producing elements in their make-up and also ages of the ruby formation using radioactive elements in small minerals trapped during ruby growth. Results revealed Mogok and Mong Hsu rubies grew at similar, but separate times, and from partly different chemical host rocks.
Eastern Australian ruby results suggest growth in altered, iron-rich host rocks and give older ages of than those for Myanmar rubies. The low-iron in Myanmar rubies resulted from growth in carbonate-rich hosts and led to a highly-prized deep red, fluorescent colour.
Myanmar and East Australian rubies differ in ages and host compositions. This produced divergent trace element budgets within the aluminium oxide crystal structure. The red, due to chromium, is less diminished by iron in Myanmar ruby to yield a superior colour.
The IMA Melbourne meeting was also attended by Ross Pogson, Collection Manager, Geoscience, and Melissa Murray Interpretive Officer, Visitor Services, who presented a survey on the Chapman Mineral Collection. The influx of overseas and Australian delegates at IMA, including museum personnel, provided invaluable new and continued interchanges of information for the Australian Museum attendees.
Dr F. Lin Sutherland, Senior Fellow