Beautiful to look at, Gem Silica is a the name for a rare form of Chalcedony crystal, which achieves its vivid green/blue colouring from the presence of Chrysocolla. Gem silica is said to enhance the power of your voice, and so is a great crystal for singers, teachers and speakers. A wonderfully calming crystal, Gem silica is said to dispel fiery energies, such as angry words and sarcasm.