image from www.woodycrt.freeserve.co.uk/sedimentary.jpg
Rocks formed by the accumulation of mineral grains settling from water. They include chemical precipitates and deposits of biological origin. The materials are derived from pre-existing rocks which have been weathered and eroded.
They are easily recognised as the rocks are usually granular and are deposited in layers. They may contain fossils and voids.
Sedimentary rocks contain sedimentary structures such as:
(There are many other structures such as those formed by living organisms from the sea!)
Sedimentary structures indicate the deposition environment and show which is the correct way up of the rock.
Return to Rock Types