What is clay?

Clay is a special type of soil because it is made of flat, microscopic particles which tend to pack in a tight, heavy mass. When wet, the particles film with moisture and cling together to form a sticky, slippery colloid. The coarse clays mixed with fertile soils, become muddy. The finer clays can be used as plastic modeling material for bricks and pottery.

All clays contain compounds of the elements silicon, aluminum, oxygen and hydrogen   plus various traces of impurities such as iron. The fine, flat fragments are powdered from rocks by water and weathering.