Hi, I was wondering if anyone could explain the following: The technology behind CD-RW discs relies upon phase change alloys usually comprising of indium, silver, tellurium, and antimony. These are translucent in their crystalline state but opaque in their amorphous state. I understand why glass - an amorphous material, is largely transparent, but why is this alloy 'the other way round' - how is it that the crystalline state is translucent? Any answer would be gratefully received. Thanks.