orthoquartzite

plural orthoquartzites

1. countableuncountableA very pure quartz sandstone composed of usually well rounded quartz grains cemented by silica.

   The contact with the Fountain is sharply defined, since they consist essentially of fine-grained red or pink to white sandstone, at time cemented to an orthoquartzite—a process still continuing.

   1928, A. J. Tieje, “The Red Beds of the Front Range in Colorado: A Study in Sedimentation”, in The Journal of Geology, volume XXXI, page 199

   2 more examples

   A similar phenomenon on a smaller scale occurs at Hole-in-the-Wall, where beds of orthoquartzite show large bulbous projections on their undersides which appear to squeeze out the underlying shale.

   1957, Keith A. W. Crook, “Cross-Stratification and Other Sedimentary Features of the Narrabeen Group”, in Proceedings of the Linnean Society of New South Wales, volume LXXXII, page 162

   In the central part of the outcrop area of the formation, a 4.5 km–wide, east-trending belt contains strata like that of the northern part of the formation except that orthoquartzite beds up to 6m thick, which commonly have strike lengths of 1–2 km, are present.

   1989, G. Neef et al., “The Mt. Daubeny Formation: Arenite-Rich ?Late Silurian–Early Devonian (Gedinnian) Strata in Far Western New South Wales”, in Journal and Proceedings of the Royal Society of New South Wales, volume 122, →ISSN, page 104