arkose (arkos)

[F.] Feldspathic sandstone; a rock consisting e entially of more or le consolidated quartzose sand with grains or particles of orthoclase di eminated through it, and frequently containing also some mica and kaolin. The feldspar seems, in some cases, to have been derived from the disintegration of rock containing that mineral; in others, to have resulted from the metamorphism of sandstone containing argillaceous material. The rock to which the name arkose has been given occurs chiefly in the Lower Silurian, Carboniferous, and Tria ic formations.