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.
Clay mineral X-ray diffraction
Well-crystallized and pure samples are ideal for x-ray diffraction, but this is rarely the case for clay. Clay minerals are almost always mixed with very small amounts of nonclay minerals which can produce intense peaks, even when there is very little of the sample is not a clay. If additional minerals are known to be presents, attempts should be made to separate clays from nonclays otherwise additional peaks should be expected. Some common minerals associated with naturally occurring clays are; quartz, feldspars, zeolites, and carbonates organic matter is sometimes present. Synthesis of clays can reduce the presence of some of these associated materials but does not guarantee pure samples as quartz or other associated materials are still commonly produced alongside synthetic clays.