A druzy is sets of tiny crystals of minerals that form on the surface of another stone. There are many types of druzy, because there are many types of minerals. Each type of druzy has particular characteristics, such as crystal size, luster and color. Quartz is one of the most common druzy types because of the prevalence of silica throughout the world. No matter what mineral forms the druzy, the overall appearance usually resembles that of sugar. The tiny crystals are considered beautiful because, like large gemstones, they glitter and catch rays of light.
The geological process that forms a druzy, the layer of crystals on the rock, occurs when water brings minerals onto a rock's surface. When the water evaporates, cooling occurs and the minerals are left behind to form crystals on top of the rock. Depending on the minerals, druzy gemstones can be almost any color of the rainbow, including white, pink, blue, purple, green or black.