Download Common Biochemical Sedimentary Rocks File

Earth Systems 3209: Common Biochemical Sedimentary Rocks
Chert
Chert is a microcrystalline or cryptocrystalline sedimentary rock material composed of silicon dioxide
(SiO2). It occurs as nodules and concretionary masses and less frequently as a layered deposit. It breaks
with a conchoidal fracture, often producing very sharp edges. Early people took advantage of how chert
breaks and used it to fashion cutting tools and weapons.
Flint, a slight variation of quartz, is often also called chert by geologists.
Coal
Coal is an organic sedimentary rock that forms mainly from plant debris. The plant debris usually
accumulates in a swamp environment. Coal is combustible and is often mined for use as a fuel.
Bituminous coal is a sedimentary rock which can metamorphose into anthracite coal.
Earth Systems 3209: Common Biochemical Sedimentary Rocks
Coquina
A poorly-cemented limestone that is composed mainly of broken shell debris. It often forms on beaches
where wave action segregates shell fragments of similar size.
Chaulk
A soft limestone with a very fine texture that is usually white or light gray in color. It is formed mainly
from the calcareous shell remains of microscopic marine organisms such as foraminifers or the
calcareous remains from numerous types of marine algae.
Coral Limestone
Calcium carbonate can also be secreted from coral or form some algae. This limestone is chemically
similar to chemical limestone, but forms from a living organism.