Granite is a hard, resistant rock, but when it is subjected to weathering it may be broken down to produce fine china clay (kaolin). Granite contains many minerals, including feldspar. When acid reacts with feldspar, it can produce kaolin. Normal rainfall is naturally acidic, and water that percolates through the soil also picks up organic acids that help to dissolve the granite. In this picture, unweathered granite is seen as solid rock, surrounded here by weathered rock.

China clay, or kaolin, is used in the manufacture of fine porcelain. The modern production method is a three-part process. First, the earth overlying the clay is removed, and a high-pressure water jet is fired at the quarry face, liberating the clay. The clay must then be sifted and refined to remove impurities before finally being dried to reduce its moisture content.