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.
Wealden iron industry
Iron ore in the form of siderite, commonly known as iron stone or historically as mine, occurs in patches or bands in the Cretaceous clays of the Weald. Differing qualities of ore were extracted and mixed by experienced smelters to give the best results. Sites of opencast quarries survive from the pre-Roman and Roman eras, but medieval ore extraction was mainly done by digging a series of minepits about five metres in diameter and up to twelve metres deep with material being winched up in baskets suspended from a wooden tripod. This was less destructive of the land as spoil from one pit was used to backfill the previous pit allowing continued land use.