Clay, silt, sand, gravel, or similar deprival material deposited by running water compacts and forms a druse or geode. A druse or geode is a hollow space that is filled by a mineral and in this case that mineral would be quartz (Amethyst or Ametrine). The geode is the section removed and the druse is still intact to be mined. The only natural occurrence of this stone is in the Anahi mine in Bolivia, and Brazil (Rio Grande do Sul).