The depositional products are those features of the rock, which resulted from the depositional event, whereas the diagenetic products are those features, which came about due to some post depositional process. The depositional products include carbonate allochems, non-carbonate allochems, terrigenous detritus, micrite, and primary porosity. Included in such are bioclasts, ooids, pelloids, and intraclasts. Bioclasts are the calcite or aragonite secretions of plants and animals of all types. Excluded are non-carbonate fossil remains.
Different organisms produce different skeletal material with differing microtextures.
Each calcite crystal has the same crystallographic orientation as the next hence all will go extinct under crossed polarizers at the same time. Sometimes you can actually see the crystal mesh-work. Brachiopods secreted calcite as microscopic rods surrounded by an organic sheath. These appear in thin section as very fine lamellae that are generally sub parallel to the exterior surface of the shell. Some brachiopods produced spines which when the spine is cut in cross section appear as a disk with the lamellae forming concentric rings around the disk.