Soil texture Soils that have a high percentage of sand, such as sandy loam, or sandy clay, have a gritty texture. Soils that have a high percentage of silt, such as silty loam or silty clay, feel smooth. Soils that have a high percentage of clay, such as clay loam, have a sticky feel. Although the texture by feel method takes practice, it is a useful way to determine soil texture, especially in the field. The hydrometer method of determining soil texture is a qualitative measurement providing estimates of the percent sand, clay, and silt in the soil. The hydrometer method was
Parent rock Parent rock Parent rock, also referred to as substratum, refers to the original rock from which something else was formed. It is mainly used in the context of soil formation where the parent rock (or parent material) normally has a large influence on the nature of the resulting soil. For example,clay soil is derived from shale while sandy soil comes from the weathering of sandstones. The term is also used in the context of metamorphic rocks where again the parent rock or protolith refers to the original rock before metamorphism takes place. Parent rocks can be sedimentary, igneous or metamorphic.