Classification of sedimentary rocks      After transportation and deposition loose sediments are consolidated into sedimentary rocks by a process called diagenesis. The sedimentary rocks thus formed may be broadly divided into two groups: Exogenetic and Endogenetic      Exogenetic  rocks are the products of fragmentation of the source rock outside the basin of sedimentation.  Endogenetic  rocks are produced out of precipitation from solution within the basin. The exogenetic and endogenetic rocks can be distinguished by their textures. While the endogenetic rocks show an interlocking or crystalline fabric (‘non-clastic’ texture), the exogenetic rocks show discrete framework grains separated by voids. The latter texture is called ‘clastic’ from the Greek clastos, meaning broken      Classification of sedimentary rocks into  clastic  and  non-clastic , though popular among sedimentologists, may at times lead ...

  What is a sedimentary texture?      The term texture refers to the pattern formed within a sedimentary rock by the constituting grains. This can best be studied under a microscope. Classification of sedimentary texture      In sedimentary rocks of  Mechanical origin , formed by weathering, erosion, transportation, deposition followed by diagenesis & Lithification, the framework grains are joined together, either by finer fragmental particles or by chemically precipitated cement. The former is called  matrix  and the latter, c ement . The pattern formed by framework grains, matrix and cement is called (a) Clastic texture . Sandstones show this kind of texture.      The texture of a rock of  Chemical origin  is produced wholly by chemically precipitated materials. No inter-granular space is to be found in such a rock. Limestones of orthochemical origin show this kind of (b) Non clastic texture .    ...