Rather ironically one of the best places in the world to buy opal jewelry, esp. high quality, is in Monterey California, not far from the Cannery. I forget the name of the jeweler but much better quality and price than I found in Melbourne. Opals are very tricky, tiny differences mean a 10 fold difference in price. You might want to look around near you in Santa Cruz or drive down to Monterey to learn as much as you can about opals. If you do buy in Melbourne it might be wise to AVOID any shop with a duty free sign in the window. Also while Melbourne shopping is generally quite good, I've found Sydney to be a lot better for opals.