Rock is a natural occurring substance which is an agglomerate of mineral particles. Rocks can be grouped into sedimentary ,metamorphic and igneous according to their mode of formation .On the side of sedimentary rock ,it is formed when sediments which are product of denudation and erosion that results from action of wind ,water and ice .Wind ,ice and water are called agents of erosion as their role is aiding the breakdown of materials into smaller fragments ,that are later transported and laid down into layers after the driving capacity is reduced where they are lithified and cemented into a solid stratified rock which is known as a sedimentary rock. Sedimentary rock is farther classified into three types according to their formation which are organically formed ,mechanically formed and chemically formed.
Organically formed sedimentary ;it is formed when the remains of once living creatures called fossils which includes bones ,shells and teeth all found in animals and leaves ,branches to mention some which are found in plants ,are compacted and cemented by a calcite to form a sedimentary as the process continues a new layer is formed above the old rock ,hence becomes stratified ,a coal is a good example.
Chemically formed sedimentary; it is the minerals combine together in a precipitate to form a rock .for instance a limestone rock is produced when water from precipitation ,like rain absorb carbondioxide producing a compound known as carbonic acid (hydrogen carbonate) which goes to react with calcium carbonate creating a weaker compound called calcium biocarbonate .When the water of crystallization is lost a compaction of rock occurs and a new sedimentary is formed ,this also explains why limestone has got unique features like staglatite staglamite , carvens and others.
(HYDROGEN+CARBONDIOXIDE) CARBONIC ACID
H2CO3 +CaCO3 Ca(HCO3)2
(CARBONIC ACID + CALCIUM CARBONATE)...