Simple test put the piece very close to your mouth and breath hard like when you clean glasses , a real diamond will clear of the fog in a matter of a second or two, where a fake stone will hold its fog much longer-up to five seconds.Do this test with a real diamond and glass stones to see the difference. I use this trick when out going through garage sales for possible unknown diamonds. They appear to be glass to me the 2 stones with the backs open are glass with gold foil backs.
