Terra Cotta, California
Coal, along with clay deposits, was found on the site by John D. Huff in the late 1880s, and the Southern California Coal and Clay Company was formed to mine them. The town site of Terra Cotta was laid out and was given a post office on October 26, 1887. In May 1893 its post office was closed and moved to Lake Elsinore. A plant for the manufacture of sewer and water pipes was built using the coal to fire ceramic pipes in the four kilns. The finished product had to be shipped by wagon six miles through Lake Elsinore to the La Laguna rail station at the mouth of Railroad Canyon until 1896 when a spur line was built through Lake Elsinore and Terra Cotta to the new clay deposits in Alberhill. The coal mined was also used locally as fuel for the stamping mill at the Good Hope Mine and was shipped elsewhere in the state.
Shrink–swell capacity
Due to the physical and chemical properties of some clays (such as the Lias Group) large swelling occurs when water is absorbed. Conversely when the water dries up these clays contract (shrink). The presence of these clay minerals is what allows soils to have the capacity to shrink and swell. Some of these clay minerals are: smectite, nontronite, bentonite, chlorite, montmorillonite, beidellite, attapulgite, illite and vermiculite. The amount of these minerals in a particular soil will also determine the severity of the shrink-swell capacity. For instance, soils with a small amount of expansive clay minerals will not expand as much when exposed to moisture as a soil with a large amount of the same clay minerals. If a soil is composed of at least 5 percent of these clay minerals by weight, it could have the ability to shrink and swell.