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.
Open-pit mining
This form of mining differs from extractive methods that require tunneling into the earth, such as long wall mining. Open-pit mines are used when deposits of commercially useful ore or rocks are found near the surface; that is, where the overburden (surface material covering the valuable deposit) is relatively thin or the material of interest is structurally unsuitable for tunnelling (as would be the case for sand, cinder, and gravel). For minerals that occur deep below the surface—where the overburden is thick or the mineral occurs as veins in hard rock—underground mining methods are used to extract the valued material.