One broker brought to me a Ruby from Myanmar recently. Observed with naked eye and even 10x loupe, the unasuming ruby has the characteristics of an unheated ruby from Myanmar ~ Silk zoning, pinkish red( Characteristic of Mogok Ruby). However, under the micro-scope, minute air bubbles along the healed fracture lines were observed ~ which indicates that this ruby had been heat treated with glass filling.
In the past, only African Ruby is treated with Glass filling. Do note that this new heat treatment had been advanced to treat on Burmese ruby as well.