Saturday, March 28, 2009
Leaded Glass Filled Ruby
A good number of years ago I walked unsuspectingly into the gem market area of Chanthaburi Thailand and saw people with piles and piles of large rubies everywhere. What were these new and plentiful gems? Many had little color for ruby and had a ghostly appearance I had never seen in a gem before. Others were top color and the prices were huge when it seemed they had just swept up after a storm of them. I did not buy any as they were far too suspect but I did meet up with a gemologist friend later that had also just witnessed the same curiosity. "Leaded glass filled" he said, "and not the kind of glass we see in flux healed rubies either"
As it turns out there were tons of ruby material in Africa that had so many fissures and cracks in it that it was basically worthless. The experienced gem treaters of Chanthaburi Thailand figured out that they could heat the severely cracked ruby with leaded glass and it was basically undetectable with gemological instruments such as refractometers, spectrometers, specific gravity readings and more. It created a somewhat marketable material especially until consumers get fed up with it and the price falls below where it is worth treating, which is a likely future event. But for now and for a good number of years yet to come, you will see beautiful glass filled rubies in places where they should not be such as in fine jewelry stores with no disclosure as to the exact nature of the enhancement. Others will and have already made it into a jewelers pickle which renders them back to a very ugly condition as the acid eats the glass.
How can we proctect ourselves from buying these short-lived beauties when we think we are buying quality rubies that will last many lifetimes? For starters, a 10x loupe can help a great deal. Often there will be bubbles in glass and that will be a huge red flag about this treatment. Not all will show bubbles with a loupe so it is not conclusive proof for no treatment, of course. Another tell tale observation with the loupe will be blue flashes. Turn the stone while looking at it with your loupe. Some leaded glass filled will show this color, natural untreated will not. One final characteristic will be slight variations in the sheen of the table, sort of like tiny wavy lines of a slightly different degree of reflection, rivers of glass. Beyond that you will need a microscope, a friend with a microscope, or a lab you can trust. The treaters know how we detect these frauds and are working to eliminate the bubbles and the blue flashes and the rivers of glass in order to create a more 'marketable' product. Buyer beware.