Clay certainly doesn’t have the appeal of gold, silver, diamonds or rubies, but it is  historically a very important resource. Many people see clay as a thicker, more moldable type of dirt, or a very small particle, but clay also describes a group of minerals. There are several individual members in the clay group. All of these minerals are sheet silicates, such as flakey mica minerals, and they all contain some amount of water in their structure. Clays have high porosity (lots of empty space) so they are able to absorb a large amount of water. This is why clay is slippery to walk on while it is raining and why it is so easy to mold. Clays are often the result of weathering of feldspar rich rocks such as granite, so they are found only near the surface of the earth. One of the most important clay minerals to ancient and modern industry is kaolinite.

Kaolinite was named after the Chinese mountain Kao-Ling, where this mineral was mined in ancient times. Kaolinite is crucial for the manufacture of Chinese porcelain and was used heavily in the 17th century for trade with Europe. Aside from ceramics, kaolinite has many other uses. It is used in paper manufacturing, in pharmaceuticals, as a filler in some foods (yes, you may be eating clay), as a binding agent in talcum powder, in toothpaste, in cosmetics and many other industries.

Clays are also important for groundwater flow. Groundwater that encounters a clay layer will be halted, as clay has low permeability (liquid flows very poorly through clay). As a result aquifers accumulate on top of clay layers, and can be pumped to supply water to communities.

To learn more about minerals, come visit the Dice Mineralogical Museum on the first floor of North Hall, open Monday, Wednesday and Friday from 1:30 to 5:00 p.m.