Ceramics consist of more than just earthenware. Porcelain and stoneware also fall within this category. Clay, the main raw material of ceramics, is created by erosion, which in a pure form contains a high percentage of the mineral kaolin. The further this sedimentary material is removed from its original location by rain, streams and rivers, the more the kaolin changes and is contaminated with other minerals. The clay used for stoneware is extracted from river sediments. Germany produces a large amount of stoneware, an example being the famous Cologne jars produced in that city. The porosity of this ceramic material lies between that of earthenware and porcelain and is baked at around 1200°C.