How can you tell a real diamond from a fake one?

I have ring i found a while ago....the mound looks fake but the diamond looks real according to all my friends. Its about the size of a large lady bug and i scratched it against some glass and it made marks. I cant tell. I dont want like myths on how you tell. I want actual scientific facts. And if its real....based on the size i said...how much do you think its worth?? Cuz i want a ipod SO BAD. lol thanks!!How can you tell a real diamond from a fake one?Real diamonds are not shiny, in fact, they are dull looking compared to fakes.

You should just take it to a jeweler at your local mall to certify its authenticity %26amp; the jeweler can also tell you an estimated price :)How can you tell a real diamond from a fake one?First of all no real diamond is going to be set in a fake setting. If the ring is gold it will be stamped on the inside with the carat. If there is no stamp then its most likely a fake. I would just take it to a jeweller and ask.