Aquamarine

Aquamarine is the blue-green variety of the mineral beryl, the same family as emerald. The name comes from Latin: aqua, water, and marina, of the sea. And the color fits: a light greenish blue, like shallow water.

The color comes from tiny amounts of iron in the crystal structure. Much of the aquamarine on the market has been heated, which reduces the yellowish tint and leaves a cleaner blue.

Aquamarine tends to grow in large, clean, well-formed crystals: long six-sided prisms, like the raw crystals in the photo. It forms in granite pegmatites and hydrothermal veins. Important sources include Brazil, especially the state of Minas Gerais, as well as Pakistan's Karakoram Mountains, Afghanistan, Kenya and Russia. According to GIA, the largest gem-quality crystal ever found was about 48 cm (19 in) long and weighed about 110 kg. Not exactly pendant material.

The largest cut aquamarine in the world is the Dom Pedro, an obelisk of about 10,363 carats carved from a crystal found in Brazil in the late 1980s. It is now on display at the Smithsonian's National Museum of Natural History in Washington, D.C.

With a hardness of 7.5 to 8 on the Mohs scale, aquamarine is well suited to everyday jewelry, and it appears both as faceted gems and as raw crystals.