(ii) Quartz Arenite Ihese are also known as orthoquartzites, which are texturally and mineralogically mature pure sandstones and show the following characteristics They are composed of quartz to the extent of 95% or more. They are presumed to be associated with the peneplanation stage of geomorphic cycles. In this case the detrital matrix is absent or less than 15% at the most. Here the feldspar as well as the rock-fragments constitute even less than 5%. They may be derived from the lithic sandstones or from, arkosic sandstones. In the former case they are characterised by metamorphic quartz and chert particles; whereas in the latter case the chert is absent or nearly so (under 5%) and the quartz is igneous- quartz.