Brazil is the world's largest producer of aquamarines, and Búzios — with its wealthy weekend visitors from Rio — has attracted a cluster of quality jewellers along Rua das Pedras. The stones come mostly from the mines of Minas Gerais state, and you can find everything from rough crystals to finely cut pieces set in gold and silver.
The range and quality is genuinely good. Aquamarine in various shades of blue is the main offering, but topaz, tourmaline, and amethyst are also common. Prices are lower than in Europe or North America for equivalent quality. If you're buying, ask to see the stone in natural daylight — shop lighting flatters everything.
Compare prices at a few shops before buying. The tourist-facing jewellers on Rua das Pedras proper tend to charge more than the smaller places on side streets.