Particles of quartz, kaolin, and lime, separately, or mixed, loose or more or less cemented, with accompanying impurities, make up the great bulk of the sedimentary rocks. They are usually arranged in layers, of varying thickness, as they were laid down by water or the wind. In the same way layered accumulations which are either products of plants or animals, or parts of the plants or animals, are considered sedimentary, as for instance, coal, chalk, petroleum, etc.
Inorganic origin: 1. Coarse fragmentary material talus resulting from weathering 2. The same fragmentary material breccia cemented 3. Unsorted material resulting from soil rock weathering 4. Coarse fragments rounded by the gravel action of water and wind 5. The same material cemented conglomerate 6. Finer material deposited by water sand or wind 7. The same material cemented sandstone 8. The finest material, mostly clay kaolin, deposited by water 9. The finest material, deposited by loess wind 10. The same material cemented shale 11. Fine particles of lime, pure or marl impure 12. The same material cemented limestone 13. Unassorted material left by the till glacial ice 14. The same material cemented tillite Organic Origin: 15. Limes made from shells, etc. coquina, chalk, coral rock, etc. 16. Silica from the shells of plants, diatomaceous earth, etc. etc. 17. Carbon from plants peat, lignite, coal, etc. 18. Hydrocarbons from animals petroleum, asphalt, amber, etc. 19. Phosphates from animals guano, phosphate rock, etc.
Where weathering is very active, especially on or below steep mountain slopes, a mass of loose, angular fragments accumulates. This material is termed talus, a term which refers only to the physical character of the material, and not at all to its composition. If weathering continues these fragments will be further broken up into one of the finer grained rocks, which the water can carry away and deposit elsewhere. There is little or no layering in talus. If the talus is not carried away but is cemented where it was formed, the resulting mass is termed breccia, but this is not very commonly the case.
The term breccia is used to cover all those rocks which are composed of angular fragments, of any composition, and above sand in size, when they are cemented into a solid mass, by any sort of cementing agent. Here the term is used in its broad sense, as compared with the way it was used under igneous rocks.