Rock Topics

Classification of Sedimentary Rocks (Part 2)

Non-clastic Texture

Non-clastic rocks have chemical or organic origins.  Names of non-clastic rocks are based on their compositions. 

• A calcite-rich rock with many fossils is called a fossiliferous limestone.

• Microcrystalline quartz is called chert.  The red variety of chert is called jasper.  Dark gray to black chert is called flint.

• The carbon-rich rock formed from ancient plant material is called coal.

Limestone and Chert
Left: fossiliferous limestone; right: chert (Photographs by Parvinder Sethi)

Coal (Photograph by Parvinder Sethi)

Sedimentary rocks with non-clastic texture include fossiliferous limestone (above left), chert (above right) and coal (right).  All three of these rock types can be found in Virginia.