Aquamarine (from Latin: aqua marina, "water of the sea") is a blue or turquoise variety of beryl. It occurs at most localities which yield ordinary beryl, some of the finest coming from Russia. The gem-gravel placer deposits of Sri Lanka contain aquamarine. Clear yellow beryl, such as that occurring in Brazil, is sometimes called aquamarine chrysolite. When corundum presents the bluish tint of typical aquamarine, it is often termed Oriental aquamarine. The deep blue version of aquamarine is called maxixe. Its color fades to white when exposed to sunlight or is subjected to heat treatment, though the color returns with irradiation.

The pale blue color of aquamarine is attributed to Fe²⁺. The Fe³⁺ ions produce golden-yellow color, and when both Fe²⁺ and Fe³⁺ are present, the color is a darker blue as in maxixe. Decoloration of maxixe by light or heat thus may be due to the charge transfer Fe³⁺ and Fe²⁺.^[6][7][8][9] Dark-blue maxixe color can be produced in green, pink or yellow beryl by irradiating it with high-energy particles (gamma rays, neutrons or even X-rays).^[10]