Siliceous rocks are
sedimentary rocks
Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles t ...
that have
silica (SiO
2) as the principal constituent. The most common siliceous rock is
chert; other types include
diatomite. They commonly form from silica-secreting organisms such as
radiolarians,
diatoms, or some types of
sponges
Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through ...
.
References
Sedimentary rocks
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