What raw materials are commonly used to make structural clay products?

Structural clay products, such as building brick, paving brick, and tile, are manufactured using a mixture of three primary natural materials:1

• Clays or argillaceous (clayey) shales (35–55 percent): These act as "formers," providing the necessary plasticity and shaping ability when mixed with water.12
• Quartz (25–45 percent): This serves as a filler, which provides structural strength to the formed object.1
• Feldspar (25–55 percent): This acts as a fluxing agent, which lowers the melting temperatures of the clay and quartz during the firing process.1

These materials are often found together in natural shale deposits, which frequently eliminates the need for extensive blending. Manufacturers typically prioritize using local clays or shales to minimize transportation costs. The final color of the product is determined by impurities within these raw materials, most notably iron oxides, which react to the firing atmosphere in the kiln.1