I saw a program on TV about this guy who would marry women, take all their money, and leave.

One of the victims was interviewed, and when she confronted the guy with doubts of his sincerity and asked whether the ring he gave her was even real, he took it and made a big scratch in a mirror with the stone to prove it was a real diamond.

Later she said, "After he disappeared, I discovered that cubic zirconia can also scratch glass"