Clay derived from brown soils or grumusol, rich with calcareous fragments, silty quartz. It is characterized by a dark, optically inactive matrix with silty angular quartz grains well- to moderately sorted. Most quarttz is angular and silt-sized, while sand-sized rounded quartz (up to 0.5 mm) appears in smaller quantities. Limestone, chalk, nari and other calcareous inclusions are also common, both silt and sand-sized. The clay is usually derived from alluvial and fluvial soils in the shephelah.