How can you tell a real ruby?
Tell by the color and the shine.
Real rubies glow with a deep, vivid, almost "stoplight" red. Fake gems are often dull: they are "light, but not bright." If the gem is more of a dark red, then it may be garnet instead of a ruby. How do you know if a ruby is real or fake? The rub test includes rubbing your ruby across a smooth (but hard) surface, like glass, and seeing if the gem leaves any color behind.