Clay is composed of flat, almost hexagonal plates with water in between. The plates can slide over each other but also stick together, so that the clay is plastic when wet. This means it can be formed easily but also holds its shape. This is not the same as an elastic material, which returns to its original shape when the force deforming it is removed...
The smaller the particles, the more plastic the clay will be. Clays have much smaller particles than sand or silt, and are only a few thousandths of a millimeter wide (0.002 mm =2 µm)...
Illite* (like mica) has three repeating layers: silica, alumina, then an inverted layer of silica, with potassium ions bonding together each group of three layers. The layers in illite are therefore bonded together more strongly than in kaolinite, which only has weak hydroxyl bonds between its layers.
*illite: a clay mineral of the muscovite mica group, with a lattice structure that does not expand on absorption of water.
No comments:
Post a Comment