Soil the mineral components of soil; it consists of rock fragments, primarily quartz particles, ranging in size from in diameter. Silt ranges in size from . Clay cannot be resolved by optical microscopes as its particles are or less in diameter and a thickness of only 10 angstroms (10 m). In medium-textured soils, clay is often washed downward through the soil profile (a process called eluviation) and accumulates in the subsoil (a process called illuviation). There is no clear relationship between the size of soil mineral components and their mineralogical nature: sand and silt particles can be calcareous as well as
Cob (material) an "unburned clay masonry" when used in a structural context. It might also be referred to as an "aggregate" in non-structural contexts, such as a "clay and sand aggregate" or more simply an "organic aggregate," such as where the cob is an insulating filler between post and beam construction. "Cob" is an English term attested to around the year 1600 for an ancient building material that has been used for building since prehistoric times. The etymology of "cob" and "cobbing" is unclear, but in several senses means to "beat" or "strike", which is how cob material is applied to a