is a siliceous
, comparatively hard, fine-grained, chert
-like, and homogeneous sedimentary rock
that is composed predominantly of the microscopic remains of radiolarians
. This term is also used for indurated radiolarian oozes
and sometimes as a synonym of radiolarian earth. However, radiolarian earth
is typically regarded by Earth scientists to be the unconsolidated equivalent of a radiolarite. A radiolarian chert
is well-bedded, microcrystalline radiolarite that has a well-developed siliceous cement or groundmass.