Even though diamonds have been rising in value year on year. Selling diamond rings still command steep discounts around 30-50%.
If you had gotten the diamond at a retailer that had buy back policy such as Brian Gavin Diamonds, James Allen etc. They would buy it back for 30% less than what you had paid. Yes that is still a big loss.
Hence, shops in HK will probably only pay half of the value since you are a foreigner and they like to rip you off. Might as well just keep it if you aren't cash strapped. If the ring is from your EX - husband or whatever, then sell that sucker at a loss OR trade it for a nice luxury second hand watch. They keep their values better over time (some only).
"Let me call my cousin who is a diamond expert. Yeah, best I can do is 5$ for that ring. It is a very generous offer that I am putting on the table. Besides, I have to pay my staff, electricity bills, rent and other to keep my shop open. Take it or leave it...... "
Sorry, if you have watched Pawn shop you might get the reference.
BUT, for the love of the poor miner who dug up your stone. Do not go to HK Pawn Shops, heard they royaly rip you off.