Conglomerate.
Vegetation in a swamp falls into water that have little or no circulation (anoxic conditions). Organic material does not completely decay and accumulates. Coal is an extrememly important source of energy, making up a majority of our electrical generation in the United States.
Many microorganisms in the ocean have skeletons made of calcite. Upon the death of the organism, these skeletons settle to the ocean bottom and accumulate. This rock is perhaps most famous for the chalk cliffs of Dover, England.
Diatomite has a history very similar to chalk, also being made of microorganisms that accumulate in the bottom of the ocean, but inthis case the skeletons have a silica composition.
Coquina is a rock made of cemented seashells. It is typically found in beach environments, especially in warm climates such as Florida, where it is extensively used as a building material.
Salts accumulate in a lake, such as the Great Salt Lake in Utah. The water evaporates but leaves the salt behind, forming a sedimentary layer.
A sedimentary rock that forms by the precipitation of calcite. Consequently, it fizzes with hydrochloric acid. Limestone can also be an organically derived sedimentary rock, caused by the accumulation and altering of seashells.
Dolomite can be very similar to limestone in appearance, but does not include large amounts of calcite and thus does not fizz with the application of hydrochloric acid. Dolomite is included on our list but is not included in our trays.
A sedimentary rock formed by the precipitation of quartz. Since it is made of quartz, it has the hardness of quartz (7) and breaks like quartz (glassy), and was used to make arrowheads.
Return to Physical Geology Syllabus
Breccia. 
Sandstone. 
Siltstone. 
Shale. 
Coal. 
Chalk. 
Diatomite. 
Coquina. 
Rock salt. 
Limestone. 
Dolomite. 
Chert.
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