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.
Ancient Egyptian pottery
The marl clay (or 'desert clay') is found along the Nile valley, from Esna to Cairo, in the Oases and at the edges of the Nile Delta. It is a yellow-white stone, which is found in limestone deposits. The deposits were created in the Pleistocene, when the original Nile river and its tributaries deposited this clay in what had previously been desert. Marl clay includes a range of kinds of clay based on their base substance. In general, they have a lower percentage of silicum and significantly higher calcium content. The most important sub-types of marl clay are:Marl clay is normally cream or white in colour when it is fired in an oxygen-rich oven. Cuts can reveal pink or orange areas. It is rich in mineral salts, so the outer surface often has a thin layer of weathered salt which forms a white surface layer when fired, which can be mistake for a 'glaze' by the unwary. At higher firing temperature (c. 1000 °C), this layer becomes olive-green and resembles a green glaze.