Lab grown rubies look like the most perfect ruby, almost fake. I have a few that my nan handed down. They were popular in Europe and usually made in Russia. Most jewelry shops sell created corundum and emeralds in Australia. They don’t have any inclusions which gives them away. Still they are technically the real deal but man made.A piece of red glass will never be equal to synthetic ruby. It doesn't have the durability of corundum. I don't have any synthetic rubies but I'm sure they have more brilliance, luster, and fire than red glass. Lab-grown ruby has the same physical, chemical, and optical properties as the natural ruby. Glass is very different than corundum.