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Ruby Prices and Fracture-Filled Ruby
Ruby is the classic colored gemstone. Ruby belongs to the same gem family -- corundum -- as sapphire. But where sapphire is a rare gem, ruby is extemely rare. And the market prices for fine ruby reflect this.
|Natural Burma Ruby|
But there is an apparent paradox in ruby prices in today's market. As the worldwide demand for ruby has increased, the supply of high quality material has declined. This has resulted in rising prices for ruby around the world. At the same time, there has been an influx of low cost ruby in the market, with large sizes offered at attractive prices. Consumers have naturally been confused!
In the past, low cost ruby has always been synthetic. Synthetic ruby is real ruby (aluminum oxide), but it has been created in a laboratory using a technique known as flame fusion. Though these synthetic rubies can look attractive, they have a very low value in the market, literally a few dollars a carat. Synthetic ruby is mainly used in cheap commercial jewelry and are not offered by any reputable gemstone dealer.
But the many low cost rubies in the current market are not only synthetic stones. Many of these cheap rubies are produced by a controversial new treatment known as fracture-filling. The treatment involves taking very low grade ruby with significant surface cracks and 'repairing' then by heating them with lead glass. The glass, which has a much lower melting point than ruby, liquefies and fills the cracks. Since lead glass and corundum have similar refractive indices, this technique improves both the color and clarity of this low grade material.
Probably 90% or more of the ruby in today's market has been fracture-filled in this way. Prices range from about $30.00 a carat here in Thailand to hundreds of dollars a carat at retail jewelry outlets. But whatever the price asked for these fracture-filled stones, they should be avoided at all cost.
The fracture-filled rubies can look attractive to the untutored consumer -- the color is red or pink-red, and stones are available in large sizes, even 10 carats. But if you look closely at these stones you will notice that they are heavily included and rather turbid with little transparency.The poor clarity is to be expected in a low cost ruby. But that is not the main problem with these stones.
|Cracks Appearing in Fracture-Filled Ruby|
A more troubling problem is the stability of the fracture-filling. Because lead glass has a much lower melting point than ruby, setting these stones can be dangerous. Since natural ruby is very hard and durable, jewelers don't usually worry about applying heat to ruby when setting a stone. But applying heat to a fracture-filled ruby can melt the glass filling, leaving a sorry looking stone full of surface cracks. Once damaged in this way, these stones cannot be repaired. There have also been reports of the glass filling being affected by common acids and household cleaners, such as ammonia, bleach and even concentrated lemon juice.
Over time, gemologists have detected larger amounts of glass in the fractured-filled rubies and some gemological labs have begun issuing test reports that describe these stones as composites rather than natural ruby. This term is certainly appropriate when the glass filling serves more as glue holding together fragments of ruby.
It is of course fraudulent to sell these fracture-filled rubies without proper disclosure of the treatment. But in our view, it is fraudulent to sell these rubies even with disclosure, since the consumer may not understand how unstable the treatment can be. When consumers buy a gemstone, they expect it will last for many years. The fragility of fracture-filled ruby makes it unsuitable for jewelry. No reputable gems dealer will sell this material and we advise customers to avoid it.
See our selection of Fine Natural Ruby