Ceramics of indigenous peoples of the Americas
The clay body is a necessary component of pottery. Clay must be mined and purified in an often laborious process, and certain tribes have ceremonial protocols to gathering clay. Different tribes have different processes for processing clay, which can include drying in the sun, soaking in water for days, and repeatedly running through a screen or sieve. Acoma and other Pueblo pottery traditionally pound dry clay into a powder and then remove impurities by hand, then running the dry powder through a screen, mixing it with a dry temper, and then mixing water to create a plastic paste. In preparing the clay, potters spend hours wedging it to remove air pockets and humidity that could easily cause it to explode during firing. The clay then needs to "cure" over time.
Mining
Since the beginning of civilization, people have used stone, ceramics and, later, metals found close to the Earth's surface. These were used to make early tools and weapons; for example, high quality flint found in northern France, southern England and Poland was used to create flint tools. Flint mines have been found in chalk areas where seams of the stone were followed underground by shafts and galleries. The mines at Grimes Graves and Krzemionki are especially famous, and like most other flint mines, are Neolithic in origin (c. 4000–3000 BC). Other hard rocks mined or collected for axes included the greenstone of the Langdale axe industry based in the English Lake District.