Fracture-filled RubyIf you're interested in rubies, you may have noticed how much of the rubies being sold by reputable dealers are described as "fracture-filled". Why is there so much of this material on the market? Is it really any good or should it be avoided? ![]() 10-Carat Fracture-Filled Ruby
To understand why these rubies are being offered, it's important to understand something about the world demand for ruby, the supply of material and the recent history of prices. Though ruby and sapphire are both corundum, ruby is much rarer than sapphire. The world demand for ruby far exceeds the supply, and some of the famous ruby deposits, such as those in Thailand and Cambodia, have been completely worked out. The same is true for the famous ruby mines of Mogok in Burma; the production from Mogok has been reduced to a mere trickle.
In 2004, a gem lab in Chanthaburi, Thailand came up with an innovation that increased the supply of ruby on the market. They developed a technique to improve the appearance of rubies of good color, primarily from Madagascar, that are disfigured by fissures or surface cracks. These previously undesirable gems could be repaired using heat treatment with lead glass. The refractive index of corundum and lead glass are very similar, allowing light to travel through the stone and improving the color and clarity. Many of the rubies that could be repaired with this new fracture-filling technique are of impressive size, with many stones over 5 carats. Since the treatment is easy to detect, it is almost always disclosed and the price is adjusted accordingly. So these fracture-filled rubies sell at a fraction of the cost of untreated rubies of similar color. In fact you won't find 10 or 15 carat untreated rubies on the market at all, and very few that have been only heat treated.
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- First Published: May-08-2008
- Last Updated: January-22-2019
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