Name the following sedimentary rocks, and describe the environments in which they might have formed. the sandstone di (8 marks) agram is provided for reference. rains are 78% quartz, 12% feldspar, 10% rock fragments, grain size 0.3 to 2 mm., grains sub-angular. a. g quartz quartz arenite (-90% quartz) compositions of arenite sandstones arkosic lithic arenitearenite | (> 10% rock fragments) (> 10% feldspar) sandstones with these compositions are rare feldspar rock fragments grains are 96% quartz, 4% feldspar, grain size 0.5 to 1 mm., grains well rounded. b.