Sedimentary rock is one of the three main rock groups and is formed in four main ways: by the deposition of the weathered remains of other rocks, by the accumulation and the consolidation of sediments, by the deposition of the results of biogenic activity, and by precipitation of minerals from solution. Some common sedimentary rocks are; chert, coal, conglomerate, dolomite, flint, iron ore, limestone, oil shale, rock salt, sandstone and siltstone.