Sandstones: clastic sedimentary rocks with grain sizes ranging from 2 to 0.06 mm. The loose sediment of the same grain size is sand. Sandstones are classified based on their depositional environment, cement type, grain size, and mineralogical composition. The most common types are: Quartz Sandstones or Quartz Arenites, containing at least 90% quartz; Arkose or Feldspathic Sandstones, with at least 25% feldspar; Graywackes, rich in silt and clay, Quartz or Feldspar; Subgraywackes, richer in Quartz than the previous type; Calcareous Sandstones with Carbonate grains; Lithic Sandstones containing rock fragments.
