What is a hard, coarse-grained siliceous sandstone; as, millstone grit; -- called also gritrock and gritstone. The name is also applied to a finer sharp-grained sandstone; as, grindstone grit called?

grit — (Geol.) A hard, coarse-grained siliceous sandstone; as, millstone grit; -- called also gritrock and gritstone. The name is also applied to a finer sharp-grained sandstone; as, grindstone grit. (Webster's 1913.)

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