Over 99% of all Ruby on the market is heat treated, to stabilize and/or enhance the color and/or clarity.  The typical heat treatment process is a permanent process that does not adversely affect the performance and durability of the gemstone, so there's no need to worry when you see this enhancement disclosed.  The typical heat enhancement procedure performed on Ruby from Sri Lanka (Ceylon) normally refers to the lower temperature wood 'blow' heat method, whereas and the typical heat enhancement procedure performed on Mogok, Myanmar, MongHsu, Thai, Vietnamese, and African Ruby usually refers to the high temperature furnace fired method.  Both heating methods are accepted trade practices, and have been for many generations.  The heat treatment process is permanent and does not adversely affect the performance, and durability of the gem, but in recent years demand for natural non-heated non-treated top quality Ruby has caused these gems to command a somewhat higher premium, depending on the gem.  We take pride in finding and featuring many of these non-heated natural Rubies.