agate 18K Opal Charm This is an opal and diamond charm purchased from agate. The setting that supports the opal has a cute design typical of agate. The setting is 18K gold (K18). As of November 11th, 18K gold is priced at over 16,000 yen/gram. The price may increase depending on market conditions. Charm only, no box or other accessories included. It has been used a few times and then stored away.