About 99% of rubies on the market are heat treated. Exposing the rubies to extremely high heat improves the rubies' clarity and in some cases, color as well.This treatment is so common, it is worldly accepted by gemologist. There is nothing suspicious at all about a heat treated ruby.
In recent years, more sophisticated treatments have arisen such as glass filling and flux healing. Basically, these methods melt out the natural inclusions and fill them with either glass are a kind of synthesis of the ruby crystal. This improves clarity as well, though these treatments are more expensive, more controversial, and less common. (For a gemstone treatment to not diminish a gemstone's value, it must be "permanent." See General Gemstone Information.)
|Heated: This is a very clear natural heat-treated ruby. Heat treated rubies are the most common and range considerably in their levels of clarity. Generally, though they are usually cloudier than man made rubies.||Created: This ruby is too good to be true: the first sign that it is probably synthetic is that it is very clear. These rubies are less valuable.||Untreated: Only a handful of rubies in the world are untreated. Large, clear rubies of good color that are untreated command extremely high prices and can only be found in the most expensive jewelry stores.|