quartzose graywacke

quartzose graywacke

[′kwȯrt‚sōs ′grā‚wak·ə]
(petrology)
A sandstone containing 50-85% quartz, chert, and metamorphic quartzite, 15-25% micas and micaceous metamorphic rock fragments, and 0-25% feldspars and feldspathic crystalline rock fragments.
A graywacke that has lost its micaceous constituents through abrasion and thus tends to approach an orthoquartzite.