Final answer:
The two main classes of clay are 1:1 clays and 2:1 clays, referring to their layering structure and the ratio of silica to alumina layers. Colors in clay are influenced by mineral content. Different societies have developed unique methods and decorations for pottery based on cultural traditions and resources.
Step-by-step explanation:
The two main classes of clay are 1:1 clays and 2:1 clays. The numbers refer to the layering structure of the clay minerals. In 1:1 clays, each tetrahedral silica layer is directly bonded to an octahedral alumina layer, whereas in 2:1 clays, there are two tetrahedral layers sandwiching an octahedral layer. Each structure creates different properties in the clay such as plasticity and ion-exchange capacity.
Certain inorganic compounds like iron oxides in clay determine its color. Iron can provide a reddish-brown hue, but other minerals can contribute to several different colors found in clay deposits. Pottery is created through various methods including hand-building, the potter's wheel and slip casting. Cultural traditions and available resources have influenced the decoration and construction techniques used for pottery, with societies like Longshan using sophisticated potter's wheels and kilns, while Early Jomon culture preferred coil pots fired in open pits.