What are glass filled rubies? These were originally low-quality ruby rough, the kind that would usually not pass for a gemstone. People think of more innovative and ingenious ways to market new products everyday, and this is exactly what happened here. Someone discovered that under certain conditions of pressure and heat, liquid glass could be inserted into the many thin fractures occupying low-end rubies. This caused them to suddenly look "clear", more transparent, and even more saturated in color at times.
Some laboratories would label these rubies as 'manufactured products'. Others would term them as 'filled rubies' or 'hybrid rubies'. Depending on the source, these stones could contain very large percentages of lead glass. The amount itself could even be more than the amount of actual ruby making up the gemstone.
Glass filled rubies are very inexpensive gems that were originally too poor in quality for jewelry use. Treatment and glass-filling makes them more marketable and transparent, but also creates durability issues and concerns.
Beware though, there are many sellers who will market these stones simply as 'natural ruby' or 'heat treated ruby'. The value of the gemstones associated with these two trade terms does not equal the value of a glass-filled ruby. Glass filled rubies are very commercial in price, while rubies treated with heat-only, are usually mid-market or could even be considered high-market, costing up to thousands of dollars per carat.
Glass-filled rubies also lose their beauty over the span of several years. The softer glass sometimes abrades or breaks up from the stone, causing cloudiness to increase and transparency to decrease. Even cleaning these stones in some high-powered jewelry cleaners can damage the internal filler slowly by slowly. It's very important to know what kind of gemstone you have, so that you can treat it with proper care and cleaning.
The best thing to consider is safety. If you feel like your stone is not what it appears to be, or not what somebody tells you it is, have it checked by a third party. Many labs can distinguish between different kinds of ruby using gemological expertise and specific equipment. Our facility in Metro Manila can always help distinguish glass filled rubies from their more valuable counterparts.
