sandstone

[Eng.sand, and stone.] Petrol. & Geol .: Any stone which is an agglutination of grains of sand, whether calcareous, siliceous, or of any other mineral nature. ( Lyell .) Siliceous sandstones are the most common. They vary in compactne from scarcely cemented sand to a hardne approaching that of quartz rock. The grains may be held together by an iron oxide, or calcareous matter, or by simple pre ure. When very fine in grain, they are called freestones; when coarse and composed of angular or subangular grains of sand, they become grits; when pebbly, pudding-stones. Loose and friable sandstones do not as a rule preserve fo ils well. They are often deeply ripple-marked, and occasionally preserve footprints or the indentations made by old raindrops. Sandstones occur in nearly every geological formation from the Cam brian to the Tertiary. Many furnish building and paving stones. [RED SANDSTONE.]