Clastic Rocks: Rock – flour obtained by the processes of weathering and erosion gets accumulated at a place in the form of layers. Over the passage of time, this accumulation organizes and takes the form of sedimentary rocks. Examples: Sandstone, Clay, etc.
Chemically Formed Sedimentary Rocks: Flowing water dissolves the soluble substances in its path, transports them and sets their accumulation elsewhere, due to which these rocks are formed. Alabaster, Gypsum , Tufa are the examples of this type of rocks. In this type of rocks, the soluble substances dissolve with water. Later when the pressure decreases, the water turns into vapor or due to decrease in the speed of flowing water, these dissolved substances start settling down, due to which these rocks are formed.