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.
Ub, Serbia
The following table gives a preview of total number of employed people per their core activity (as of 2016):
There are several mines and resource centers of coal (Radljevo field - 344,000,000 tones, Zvizdar field - 280,000,000 tones), clay, sand, stone and limestone.
The biggest producer of quartz sand in Serbia is "Kopovi a.d.", with overall production of over 400,000 tones per year. 
Clay pits are based below the layers of sand and quartz sand. Municipality of Ub is the biggest supplier of high-quality clay in Serbia. There are more than 1,800,000 tones of clay.