A dark grey outer shell with white and clear crystal structures. Ranging from bulbus, to thick dense crystal build up.
"Mexican “Trancas” geodes are surface mined about 220 miles south of El Paso, Texas in Chihuahua province, Mexico. These particular geodes contain primarily clear or drusy quartz linings and may also have calcite, fluorite, and quartz scepters as well."
"Geodes are geological rock formations which occur in sedimentary and certain volcanic rocks. They are essentially rock cavities or vugs with internal Crystal formations or concentric banding. The exterior is generally Limestone while the interior contains Quartz Crystals and/or Chalcedony deposits. If the Geode is completely filled with Crystal, being solid all the way through, it is then called a nodule." - https://therockshed.com/geodes.html