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Sedimentary rock
Clastic Chemical Organic
Formed from pieces of weathered rock which have been cemented together
Weathering•Bits of rock are broken
off, these are called ‘sediments’
Deposited•The sediments travel down a
river and are deposited at the bottom of a lake or ocean
Compaction•Over time the pressure
of the water pushes the sediments together
Cementation•The sediments end up
stuck together, forming a rock
Lithification
Depositing
See this animation (and more information!) at: www.classzone.com
Compaction / Cementation
Properties
has layers, the layers are obvious when looking at a large rock face
grains in the rock do not interlock, because they were cemented together
may contain fossils such as shells
Breccia
Clastic Sedimentary Rock
Very large rocks (rough edges as they have not been transported very far) cemented together
Conglomerate
An example of a clastic sedimentary rock
Large rounded rocks cemented together
Sandstone
An example of a clastic sedimentary rock
Moderately fine particles cemented together
Shale
A fine-grained clastic sedimentary rock
Very fine particles cemented together
Formed from minerals crystallising from a solution
Remember what is left behind after evaporation? That stuff!
Properties
most have crystals in them
quite soft
rare to see any layering
occasionally contains fossils
Limestone
An example of a chemical sedimentary rock
Contains a whole lot of Calcium Carbonate, so it will fizz if you put acid on it.
It’s also useful for making cement!
Limestone is very susceptible to weathering
Formed from dead animal or plant material
Properties
Can be layered, depending on the way in which the fossils and sediments are deposited
Usually soft, although a few (such as flint) are hard.
Limestone
YES! It’s also an organic sedimentary rock
Many animals have parts (shells, etc) which consist of the same chemical that makes limestone!
Coal
An example of an organic sedimentary rock
Limestone - paving, walls, buildings (unfortunately weathers quickly), making cement, glass and steel
Sandstone - buildings, easy to carve for decorative features, walls, foundations, paving, making glass
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