A geode starts as a hollow cavity inside a rock. In sedimentary rocks, cavities can form from the dissolution of minerals like limestone or from decaying organic material.
   Over time, mineral-rich water seeps into the cavity through tiny pores or cracks in the surrounding rock. The dissolved minerals start to crystallize along the interior walls of the cavity. As more mineral-rich water flows through, additional layers of crystals slowly build up. The specific minerals present (such as quartz, amethyst, calcite, or celestite) determine the colors and crystal formations inside the geode. The geode formation process continues as long as mineral-rich water is available. Eventually, the cavity may completely fill with crystals or remain partially hollow, leaving behind a stunning mineral display. This specimen weights 100 g(3.5 g), with mineral stand included. It has a couple minor scratches thsat did not polish out so well, hence the lower price.