clastic sedimentary rocks

• Breccia is a course grained clastic rock that is not generally transported long distances and has angular clasts.
• The coarse grains in breccias are often mixed with finer grains and set in a matrix, making them poorly sorted.
• Breccias can form scree, alluvial fans and wadi deposits.
• Conglomerate is a coarse grained clastic rock that is often transported long distances and is rounded.
• The large clasts in conglomerates can also be surrounded by fine grained matrix and are poorly sorted.
• Some conglomerates are held in place by a mineral cement.
• Conglomerates can be found on beaches and where river channels deposit sediment.
• Sandstones are 0.06-2mm in grain size and are used in building stone.
• Sandstones can be very porous which means they are poorly cemented or they can have a low porosity which means they are well cemented.
• The main mineral in sandstones is quartz but they contain mica and k feldspar.
• Orthoquartzite is a sandstone made of 90% quartz with grains held together by a quartz cement.
• Orthoquartzite has well sorted and rounded grains, indicating it has undergone extensive weathering and is often found at beaches and shallow marine deposits.
• The clasts in desert sandstone are cemented together by silica or iron minerals and is often found in arid environments.
• Arkose is a medium grained sandstone that is made from mostly quartz and 25% feldspar.
• Fine grained clastic rocks are deposited in low-energy environments and are the most abundant, often containing fossils.
• Clay grains are very small and can come in a variety of colours.
• Mudstones are very fine grained and contain quartz and mica, are not plastic and do not layer.
• Shale contains very fine grains that make distinctive layers, is hard and brittle, and can be described as fissile.