<human>: Can you condense the text into three sentences or less?

My mom promised me my great-grandmother's diamond to be set in a ring when I propose to my girlfriend. The diamond was originally in a ring, but then converted to a necklace. 

My mom took the necklace to Gold Buyers of America to be removed from the gold and they chipped the perfect diamond, unbeknownst to my bad eyesight mom! The guy even said to her that it was really difficult to get out of the setting, so I believe he knew he chipped it and just didn't tell her.

Now, after the fact, I took the diamond back to them to show the chip and they claim they can do nothing for me, since I can't prove they chipped it!

What can I do?
<bot>: Cash for gold place took diamond out of necklace and chipped it in the process w/o my mom seeing. They won't do anything to pay back since we can't prove it!