Druzy, also know as -- druse, drusy, drusies. They all mean tiny quartz crystals that form within or on the surface of other stones. When ground water carrying dissolved silica is forced into a porous area of the rock, rapid cooling often occurs, causing the formation of tiny crystals on the surfaces or in cavities of the rock. The clear crystals often form on top of previously deposited minerals. This is called a druzy.