Diamonds International is a good stop on any of the "islands". They have a New York office also. Remember that if you purchase loose stones you do not have to pay any duty on them when you come back into US. Set stones you do. We did not do our homework before we left and even though we felt like Diamonds International gave us some good advice, we declined the purchase in Mexico. At that time we were looking for a single stone 1 ct or more to do a new wedding set. (anniversary present) We happened to be shopping in the gift shop on the Carnival Inspiration and found some beautiful diamond stud earrings set in white gold. The staff was very knowledgeable and gave us more info than in Mexico. We bought them, I love them and we were provided with all the paperwork from the gift shop. We know the color, clarity, carat, etc. I showed them to my jeweler when we got back and he said we made a good purchase. He would have actually rated them higher in color than Carnival did...........I was very pleased and we have a guarantee from them. All this to say, maybe check out the gift shop also before you go into St. Thomas or St. Maarten, look at their selection, get a mini lesson and prices and then decide. I know we will.................Two things that my jeweler did tell me. Sometimes the loose stones (usually amethyst, topaz, that kind of stone) are cut a little differently and might require a custom made setting to get them to fit AND when you buy set diamonds, many times the clarity may be rated lower because of an inclusion that might be under a prong. If you are buying them to wear he said not to shy away from a lower clarity if the inclusion is under a prong OR can be set under a prong. You get just as pretty a stone, bigger and whiter probably for less money and no one will know if that little white spot is under a prong. Also with earrings, I didn't know this but everyone else probably does, there is a setting called a "martini" setting. It's three prongs and if you hold up the earring sideways it does look like a martini glass. These as pierced earrings will sit in the hole in your ear closer. Jeweler said people get these so that earring doesn't protrude from the ear. It sits REAL low in the hold in your ear, perfect for a second hole or someone who has real long hair. I told you more than you wanted to know didn't I??