[name] Beryllium [intro] Beryllium forms a passivating oxide layer and does not react with air or water. It is lighter than aluminium, yet it is much stronger. Consequentially, it is used in a wide range of applications, like aerospace, mirrors, military ... Furthermore, Beryllium is virtually transparent to X-rays. It is also used in nuclear reactors to reflect and absorb neutrons. Another interesting application area is acoustics. The combination of high rigidity and low density makes Be a useful material for high-end high-frequency speaker drivers. While Be is very useful, its processing and commercial use poses some technical challenges related to the toxicity of Be-containing dusts. Be can cause a chronic life-threatening allergic-type lung response called berylliosis. [image] This is the box with which we started in 2011 in our periodic table. The pure metal is encapsulated in glass. The second object is a mineral aquamarine containing Be. It is translucent when illuminated. The last object is an application for radiation windows in X-ray tubes.