siliceous sandstones are excellent examples of this permanence.
Because of their common gangue of quartz these are often called "dry" or "siliceous" ores.
siliceous materials, those composed of flint or quartz, although hard, are brittle and deficient in toughness.
In general, their siliceous shells are firmer and more massive, usually also somewhat larger, but of simpler structure.
Some of the siliceous rocks of this formation are used extensively for millstones.
The siliceous bars and beams constituting it are invariably solid (as also in the Spumellaria); never hollow (as in the Phodaria).
Their bodies are sometimes naked, sometimes covered with a siliceous, chalky, or membranous cuirass.
It was manifest especially in the siliceous stratum before-mentioned.
Generally speaking, the composition of the infusoria of the Atlantic are calcareous; those of the Pacific, siliceous.
In clays also siliceous and calcareous concretions are often found.