Beautiful translucent 'Sand and Sea' gem silica earring pairs. So, what is gem silica? According to the GIA: Gem silica is a bluish green to greenish blue variety of chalcedony that receives its vivid color from the presence of copper. It is often known as "chrysocolla chalcedony" or "gem silica chrysocolla." It is a rare occurrence in nature and why it's not often seen in mainstream jewelry.