Improving the quality of gemstones by treating them is common
practice. … The most common treatment is the application of
heat. Most rubies at the lower end of the market are heat treated to
improve color, remove purple tinge, blue patches, and silk. These
heat treatments typically occur around temperatures of 1800 °C (3300
I'm glad I wasn't the person who first decided to find out what would
happen when you stick rubies in a 3300-degree oven.