About The Mill
The Mill is located 50 miles east of San Diego on Highway 94 in the township of Campo. It also is on the San Diego-Imperial Valley railroad line. The Campo Mill is a100-foot (9 stories) tall building and was built in 1925 by Standard Sanitary Manufacturing Company to process a mineral called Feldspar. In 1918 Feldspar was discovered in Hauser Canyon (5 miles north of Campo) by William Stell of El Cajon and the claims were patented in 1924. These claims were sold to the Standard Sanitary Manufacturing Company in 1925. Feldspar was trucked to the Mill and ground to a fine powder (200 mesh). It was then loaded into railroad cars and shipped to Richmond, California to make Porcelain. Porcelain is used to make bathroom tubs, sinks, and toilets. The Feldspar was also used to make glass, pottery and soap.
Feldspar has been used in ceramics in China since the Tang Dynasty (621-945 AD) and in Europe since the 18th century. United States first mined Feldspar in 1825 in Connecticut and was shipped to England for use in ceramics. In 1911 Feldspar was discovered in Mitchell County, North Carolina where they became the major producer. Then, in the 1930's California became the major producer of Feldspar.
Feldspar is a general name for a group of anhydrous aluminum silicate minerals which contain varying amounts of Potassium, Sodium and Calcium. These are the most abundant minerals in the Earth's crust. Feldspar fuses at lower temperatures than other ingredients. It therefore acts as flux by wetting the solid particles and the surface tension pulls them together. It also increases strength, toughness and durability. 50% of glass is made up of Feldspar, 30% in ceramics, 4% in enamel and 11% in soap.