Greensand

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This article is about the sedimentary rock, greensand; for the sand used in casting, see Green sand

A roadcut near the Llano Uplift exposing Cambrian greensand in the lower unit. Notice the normal fault cutting through the formation.

Greensand is an olive-green coloured sandstone rock which is commonly found in narrow bands, particularly associated with bands of chalk and clay worldwide; it has been deposited in marine environments at various times during Earth history, such as during the Jurassic and Cretaceous periods.

1 Formation and Locations
2 Properties and Uses
3 External links
4 See also

[edit] Formation and Locations

Greensand forms in anoxic marine environments that are rich in organic detritus and low in sedimentary input. Greensands are occasionally fossil-rich, such as in the late Cretaceous deposits of New Jersey. Important exposures are known from both North America and Britain; in Britain, "greensand" usually refers to a specific geologic formation. In some areas, a distinction is made between Upper Greensand and Lower Greensand; these strata tend to occur just beneath the Chalk and can be separated by a layer of Gault. Greensand is quite common in northern and western Europe. In Britain, prominent seams are to be found in the Vale of White Horse, the Greensand Ridge in Bedfordshire, the Greensand Way in Kent and the Jurassic Coast in Dorset.

[edit] Properties and Uses

The green colour of greensand is due to variable amounts of the mineral glauconite, an iron potassium silicate with very low weathering resistance; as a result, greensand tends to be weak and friable. It is a common ingredient in garden fertilisers, such as in organic gardening and organic farming. Due to its chemical exchange properties, the glauconite of greensand is used as a water softener. Greensand coated with manganese oxide, known as manganese greensand, is used in well water treatment systems to remove insoluble ferric (oxidized) iron and manganese.