* Source: Arkose sandstone is typically derived from the weathering of granite or other felsic igneous rocks. These rocks are rich in feldspar, which is a relatively unstable mineral. Feldspar breaks down quickly during weathering, resulting in angular fragments that don't have time to become rounded. Quartz, on the other hand, is a much more resistant mineral and can withstand weathering for longer periods.
* Transport: Arkose sandstone usually forms close to the source rocks, meaning the sediment has not been transported far. This limited transport means the grains haven't had a chance to be abraded and rounded by friction during movement. In contrast, quartz sandstone often forms from sediment that has been transported long distances, allowing for more time for the grains to be rounded.
In summary: Arkose sandstone's angular grains are a direct result of its origin from unstable minerals like feldspar and its limited transport distance, whereas quartz sandstone's rounded grains are due to the resistance of quartz to weathering and the longer distances it can be transported.
