Decomposed granite Decomposed granite Decomposed granite is classification of rock that is derived from granite via its weathering to the point that the parent material readily fractures into smaller pieces of weaker rock. Further weathering yields material that easily crumbles into a mixtures of gravel-sized particles known as grus, that in turn may break down to produce a mixture of clay and silica sand or silt particles. Different specific granite types have differing propensities to weather, and so differing likelihoods of producing decomposed granite. It has practical uses that include its incorporation into paving and driveway materials, residential gardening materials in arid
Eluvium Eluvium In geology, eluvium or eluvial deposits are those geological deposits and soils that are derived by "in situ" weathering or weathering plus gravitational movement or accumulation. The process of removal of materials from geological or soil horizons is called eluviation or leaching. There is a difference in the usage of this term in geology and soil science. In soil science, eluviation is the transport of soil material from upper layers of soil to lower levels by downward precipitation of water across soil horizons, and accumulation of this material (illuvial deposit) in lower levels is called illuviation. In geology, the