siliceous

Siliceous is an adjective used to describe materials, rocks, sediments, or organisms that contain silica (SiO2) or have silica-based structures. The term derives from the Latin silex, meaning flint, with the suffix -ous.

In geology and sedimentology, siliceous rocks are those with a high silica content, typically dominated by quartz. Common examples include chert and flint, which are microcrystalline quartz, as well as opal, a hydrated form of silica. Siliceous sediment can take the form of diatomaceous earth or radiolarian ooze, formed from the microscopic skeletons of silica-secreting organisms. When such sediments accumulate and become lithified, they can produce siliceous rocks like chert, or contribute to silica-rich layers within sedimentary sequences.

Biology also uses the term siliceous to describe organisms or structures made of silica. Diatoms and radiolarians build intricate siliceous skeletons, and some sponges possess siliceous spicules. The presence of siliceous organisms influences the silica content of marine sediments and the mineralogy of resulting rocks.

Siliceous materials have distinct physical and chemical properties, such as high hardness and chemical stability in certain environments, which influence their behavior in geological processes like diagenesis and cementation. They also have significant industrial importance in products such as glass, cement, and abrasives, reflecting the wide relevance of silica-rich materials in both natural and human contexts.