Cements:
- Typical cements found in clastic rocks:
- Silica (SiO2)
- Calcite (CaCO3)
- Hematite (Fe2O3)
The major difference between sediment and a sedimentary rock is that sedimentary rocks have been lithified by a cement. Once it precipitates, the cement holds together what was loose grains of sediment.
These are typical cements because these molecules are fairly abundant in nature, and are thus commonly found dissolved in water. When water gets in between grains of sand (for example), a cement will begin to precipitate. (much like material that precipitates on the interior of pipes). Eventually, with enough precipitation, the cement will essentially “glue” the grains together.
