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.
Mining industry of Angola
Angola is also rich in several other mineral resources that had not been fully exploited by the early twenty- first century . These include manganese, copper, gold, phosphates, granite, marble, uranium, quartz, lead, zinc, wolfram, tin, fluorite, sulfur, feldspar, kaolin, mica, asphalt, gypsum, and talc. The government hopes to resume mining in the southwest for crystalline quartz and ornamental marble. It has been estimated that 5,000 cubic meters of marble could be extracted annually for a period of twenty years. A state-owned company mined granite and marble in Huíla and Namibe Provinces, and in 1983 it produced 4,450 cubic meters of granite and 500 cubic meters of marble. Since then, the company has ceased production in order to re-tool with modern machinery. Quartz production, however, was suspended indefinitely because of the military situation in areas near the extraction sites in Cuanza Sul Province.