Kaolinit, Kalzit, Quarz, St. Francisville, Warsaw geodes, Clark Co., Missouri, USA https://commons.wikimedia.org/wiki/File%3AKaolinite%2C_Calcite%2C_Quartz-400223.jpg–von John Krygier (http://www.mindat.org/photo-400223.html) [Public domain], via Wikimedia Commons