Rock Topics

Composition of Sedimentary Rocks (Part 1)

Sedimentary rocks are also classified based on their mineral composition.  Common minerals in sedimentary rocks include:



Clay minerals


Gypsum and halite

Feldspar and mica


Quartz is an extremely stable mineral, both mechanically and chemically.  It is a major component of sandstone and chert.  This photograph shows a sample of chert. 

Chert Chert (Photograph by Parvinder Sethi)


Calcite forms limestone through chemical and biological processes.  Limestone is a very common sedimentary rock.  The small gray mineral grains and the white fossil grains in this rock are both composed of calcite. 

Fossiliferous limestone
Fossiliferous limestone (Photograph by Parvinder Sethi)