Powerball geode pair small (colored) 5-8 cm light outside and Amethyst-colored purple inside.

Geodes are rock formations that are unremarkable on the outside, but contain hidden crystals inside. 'Geode' in Greek means 'earth-shaped', and geodes can be round or oval. Their size varies from a few centimeters to meters. It can take millions of years for the largest crystals to form. The types of minerals that occur as crystals in a geode vary by location and conditions such as temperature, acidity and the type of rock in which they form. For example, quartz crystals are common in volcanic geodes. Geodes can also contain a variety of other minerals. The bands and colors of geodes are the result of varying impurities; for example, iron oxides can give rust colors to silicon-rich solutions. While most geodes contain clear quartz crystals, some have purple amethyst crystals. Others may have bands of agate, chalcedony, or jasper, or crystals such as calcite, dolomite, celestite, and so on. There is no easy way to determine what is inside a geode until it is cut open or broken. Geodes and geode disks are sometimes artificially colored. Specimens with unusual colors or unlikely formations have often been synthetically processed.