The blue variety of the mineral Beryl

Hardness: 7 1/2 to 8
Toughness: good
Color: Greenish-blue to blue-green, usually light in tone
Usually eye clean and commonly available in large sizes
Stone for March and Pisces

Care:
Ultrasonic: usually safe
Steam: usually safe
Warm, soapy water: safe

Stability:
Heat: generally not heat sensitive unless liquid inclusions are present
Light: stable
Chemicals: attacked by hydrofluoric acid

Common sources:
Brazil, Nigeria, Zambia, Madagascar, United States, Russia

Treatments:
Aquamarine is routinely heated to remove the greenish cast. The treatment is common, stable, and usually undetectable.