How can you tell if a diamond is a real diamond? Would they insert a fake in real gold?

I have a necklace, not sure where I got it but it is 14K gold along with the chain it’s on. It also has a diamond in it but I can’t tell if the diamond is real. I know they have lots of diamonds that are cubic zirconium’s or diamond-aura’s but how can I tell [...] http://bit.ly/ccg3M8