Composite rubies must be distinguished from other rubies, and it is important to understand what types of rubies are now available in order to grasp the full picture. Today there are two general categories of gemstones, including ruby: treated and natural (that is, not enhanced in any way). Rubies have been routinely enhanced by a variety of techniques for almost half a century, and are well accepted within the trade. The most common type of treatment for ruby is heating, which improves the color and clarity to varying degrees. Today anyone buying a ruby should assume it’s been heated (and possibly treated in other ways) unless there is documentation from a respected laboratory confirming that it is entirely natural...More at the link. The photo above shows the air bubbles in a composite "ruby."
But "treated" rubies should not be confused with "rubies" made from multiple pieces of low-quality corundum fused together with tinted glass." "Treated" rubies are single stones that have been improved in some way to look more attractive. Some were lovely even prior to treatment, the treatment simply having made them even more attractive. Composite rubies are an altogether different thing, much less durable, and of much lower value.
Composite rubies began to surface in the USA in 2008. By early 2009 they were appearing in disturbing numbers, often among military personnel returning home with sparkling "treasures" purchased at "bargain prices" while "close to the mines," never suspecting they were victims of a scam. Today they are being sold in department store chains, mass-merchandisers, on the internet, television shopping channels, and at auction. In most cases, the prices seem to be "bargains" by comparison to the cost of other rubies sold in other stores, when, in fact, nothing is farther from the truth. Since they are not genuine rubies, there can be no comparison...
And while researching this, I encountered a story this week that a class action lawsuit is being filed against Macy's for selling glass-filled "rubies" and other bogus gemstones. The world of diamonds and colored gemstones is a minefield for the unwary - enter with care.