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Glass Filled Ruby


Glass Filled Ruby  


Yes, many Rubies are glass filled, especially those coming from Madagascar and Mozambique. This is similar to the oiling of Emeralds, and improves the clarity of the gemstone by filling cracks. Unlike Oiling, this glass filling is more stable when ultrasonic and/or steamed cleaned.

However, the trade does believe that treatments/enhancements should be disclosed. Since we have known that many Rubies are glass filled, our finer important Rubies like our Burmese Rubies, have been tested and the reports indicate heating (expected for the most part, as most Sapphires are also being heated as well as most tanzanites to create that blue purple color.

Aquamarines are typically heated to drive off the yellow component leaving a more true blue color behind). We don't feel that heat is really an issue unless someone seeks a non-heated gemstone.

Virtually almost all rubies selling in the gem market today are treated in some manner. Heating is used mostly to:

•             Develop or intensify a ruby’s color

•             Remove or decrease banding or zoning

•             Reduce modifying hues

•             Improve clarity by removing or reducing inclusions, or by making them less visible

These modifications can dramatically affect to ruby’s appearance and value.

•             Thai rubies drop their brownish color.

•             Sri Lankan rubies become a more intense red.

•             Mong Hsu rubies lose their blue centers, or cores.


Sometimes, for marketing purposes, heating is called “the continuation of a natural process.” However, this is misleading since there are no computer-controlled ovens in nature. GIA, as well as the Jeweler’s Vigilance Committee, advocates disclosing all treatments.

For most the Burmese Rubies we came across, they have been heated in borax which acts as a flux and if there are any pits, scratches, etc. the borax will fill in these voids. The reports usually indicated the slightest 'filler' which in these cases usually just the borax filling in voids, and it is not glass. In fact, we have a beauty of a Burmese Ruby that did test out as having filler, but this is borax and the amount was nothing to be concerned about.



Rough Möng Hsu ruby before (left) and after (right) heat treatment

However, the glass filling is used for typically the poor quality Ruby to make it marketable. At times, there may be more glass than Ruby! This is something that we have stayed away from - though for some in the trade as well as consumers, having a very large Ruby that has passable inclusions and is glass filled, is ideal because of the price usually associated with it, but the seller should disclose this fact. All this said, it sometimes pays to know the exact questions to ask when it comes to specific gemstones.


Ruby rough before treatment

Ruby rough after treatment

Identifying Glass filled Ruby 

Surfacing cracks is typically seen on the surface of many lead glass filled ruby.


 Flash Effect when look parallel to the fracture plan is one of the strong identification of being filled with lead glass.

In the case of Ruby, a simple question of - "Is it Natural Ruby" is not enough. Answering “Yes” from many sellers may indeed be correct - it is a natural Ruby, BUT, it may have been Glass Filled, Heated, etc. Glass Filling or Heating has nothing to do with Natural Origin - so the seller would have been correct if the Ruby was indeed natural and mined from the ground. It is the disclosure that is the issue.

The other issue with asking questions about treatment, natural origin, etc. especially in a store (and in the case of a large retail store such as Macys), is that the person providing the information just doesn't know. That information is typically lost or never even disclosed. They might know that it is a Natural Ruby, but the origin and any treatments are beyond their knowledge. This is even beyond the scope of many selling gemstones in the very countries where dealers like me make purchases to disperse gemstones to the public and the trade throughout the world.  

 This is why it is advantageous to purchase gemstones from those in the know, who travel the world and see/read what goes on out there. Buying from those mining the rough gemstones or purchasing with only one source between the miners provides All That Glitters with insight to where something originated, what treatments might have been applied. If we have concerns, we will have it certified for verification of what we were told or what we believe or suspect.