Organic Sedimentary Rocks 

Organic sedimentary rocks are rocks made from organic matter. Organic matter can be leaves, roots, shells and other parts of living organisms.
Coal is an example of an organic sedimentary rock. Coal is made from dead plants ,leaves, roots that accumulated and was buried under layers of sediment. Over time due to heat and pressure this decayed mater is transformed into organic sedimentary rock.
Fossiliferous limestone is another example of organic sedimentary rock. It is composed of fossils which were compacted and cemented into a rock.