Aquamarine is a type of beryl, which makes it a close cousin of the emerald. Unlike emeralds, though, aquamarines are relatively common. Dark-blue varieties are found in Nigeria and Madagascar, while the best paler-blue examples come from Mozambique and especially Brazil. In the United States, aquamarine is mined in Wyoming and Colorado, but it has been found in just about all 50 states.

Although aquamarines are often step cut like emeralds, the gemstones have greater clarity, which makes them suitable for brilliant cuts, too. The most desirable aquamarines are free of inclusions. Another characteristic of aquamarine for those who enjoy wearing fine jewelry is that the stone actually looks better under artificial light than daylight, making it a good choice for dinners and other evening events.

Most people associate aquamarines with the color blue, but many are sea green and almost all aquamarine in its natural state has some green in it. Ferric iron is responsible for ...the hue, so the stones are usually heat-treated, which eliminates the green and leaves a rich, blue tone. When it comes to aquamarines, tone is a major factor in price, with dark, but not too dark, blues fetching the highest prices.