Sandstone is composed of quartz grains, which are stable in structure, usually light brown or red, mainly containing silicon, calcium, clay and iron oxide. The sandstone is a sedimentary rock composed mainly of sand cement and the sand content is greater than 50%. The vast majority of sandstone is composed of quartz or feldspar.
Mudstone is a kind of sedimentary rock solidified from mud and clay, and its composition and structure are similar to that of shale. Mainly composed of clay minerals (such as water mica, kaolinite, montmorillonite, etc).
Limestone is virtually constructed by pure calcite, the content of other components often below 5%, which is more common is clay minerals, quartz sand powder, iron particles, glauconite, organic matter.