Conglomerate is a coarse-grained
clastic sedimentary rock that is composed of a substantial fraction of rounded to subangular
gravel-size
clasts, e.g.,
granules,
pebbles,
cobbles, and
boulders, larger than in diameter. Conglomerates form by the
consolidation and
lithification of gravel. Conglomerates typically contain finer grained
sediment, e.g., either
sand,
silt,
clay or combination of them, called
matrix by geologists, filling their interstices and are often cemented by
calcium carbonate,
iron oxide,
silica, or hardened clay.