aquamarines

Aquamarine is the blue to blue-green variety of the mineral beryl (Be3Al2Si6O18). Its color, which ranges from pale blue to vivid blue-green, is caused by trace amounts of iron, typically Fe2+. The name comes from the Latin aqua marina, meaning sea water.

As a member of the beryl family, aquamarine shares the same chemical composition and crystal structure, forming in hexagonal crystals. It has a Mohs hardness of 7.5–8, a specific gravity around 2.68–2.74, and refractive indices near 1.577–1.583 with weak birefringence. The gemstone is usually transparent to translucent and displays pleochroism, appearing blue from one axis and colorless to pale blue from the perpendicular axis. It has imperfect basal cleavage.

Color can be enhanced by heat treatment, which often removes greenish tones and deepens the blue. Treated stones are common in the market and generally stable. Some stones may be irradiated to adjust color, and such treatments should be disclosed by sellers. Untreated stones with strong blue coloration are typically more valuable.

Aquamarine occurs in granitic pegmatites and, less commonly, in hydrothermal veins. Major sources include Brazil (Minas Gerais), Nigeria, Madagascar, Zambia, Russia, Afghanistan, Pakistan, and the United States (notably Colorado and Maine).

In jewelry, aquamarine is popular for its clarity and calm blue color and is cut in faceted shapes or emerald-cut styles. It is relatively durable but can be damaged by sharp blows or sudden temperature changes; cleaning with warm, soapy water is advised, and ultrasonic cleaners should be avoided if the stone has fractures or visible inclusions.