Mohs Hardness of 7.5-8 with a hexagonal crystal structure.
Aquamarine belongs the the Beryl family of stones and is a cousin to the Emerald. A great many Aquamarine gemstones on the market have been treated with heat to enhance the depth and / or hue of it’s color. Therefore care must be taken not to overheat an aquamarine stone that one may have, as they may loose their color entirely. This heat treating practice came to being as the Aquamarine is one of the few gemstones that have never been successfully synthesized or duplicated.