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.
Medicinal clay
The effects of weightlessness on human body were studied by NASA in the 1960s. Experiments demonstrated that weightlessness leads to a rapid bone depletion, so various remedies were sought to counter that. A number of pharmaceutical companies were asked to develop calcium supplements, but apparently none of them were as effective as clay. The special clay that was used in this case was Terramin, a reddish clay found in California. Benjamin Ershoff of the California Polytechnic Institute demonstrated that the consumption of clay counters the effects of weightlessness. He reported that "the calcium in clay ...is absorbed more efficiently ... [clay] contains some factor or factors other than calcium which promotes improved calcium utilization and/or bone formation." He added, "Little or no benefit was noted when calcium alone was added to the diet."