Beryllium's atomic number is 4 and its symbol is Be. Beryllium is a lightweight and brittle metal that can be extracted from naturally occurring minerals and gemstones. Gemstones that contain beryllium include aquamarine, emerald, and chrysoberyl. Because of its high conductivity, high strength, and low weight, it is a favorable material in the aerospace industry. However, this metal is perhaps one of the most difficult metals to safely machine. If inhaled, beryllium dust can cause a chronic life-threatening illness known as Chronic Beryllium Disease. This makes it an extremely difficult metal to machine and process safely. Intense precautions must be taken by those who work with and process beryllium. That said, this element is perfectly safe as a solid chunk, especially once it is embedded inside the crystal-clear Lucite acrylic cube. Beryllium is also used to make non-sparking and non-magnetic tools, high-end speakers, and lightweight mirrors for satellites. The beryllium metal in these acrylic cubes was obtained in pellet form and each cube contains approximately 1-2 grams of metal.