4 x 4 x 5cm Agate is a translucent form of microcrystalline quartz. These crystals form inside of igneous rocks over a long period of time and get their banding from years of siliceous groundwater building up in the cavities of these rocks. What makes this mineral so beautiful and unique is that the color variations and banding patterns are completely dependent on the environmental factors around them. This makes it so that every formation is different and there are no two formations that are the same! ***Due to natural variations in stones, the appearance will vary***