(Originally) a quartzite formed from sandstone by infiltration and pressure; (now) an unmetamorphosed sedimentary rock consisting of quartz grains cemented with silica.
Origin
1920s; earliest use found in Journal of Geology.
Definition of orthoquartzite in US English:
orthoquartzite
noun
Geology
(Originally) a quartzite formed from sandstone by infiltration and pressure; (now) an unmetamorphosed sedimentary rock consisting of quartz grains cemented with silica.