Answer :
Sand dunes are dominated by quartz grains because quartz is highly resistant to weathering and erosion, and it does not have cleavage, which makes the grains durable and resistant. These grains are also rounded and sand-sized, making them suitable for wind transport. The constant environmental movement results in well-sorted, homogeneous quartz-rich sands that form dunes.
Sand dunes are typically dominated by quartz grains because quartz is highly resistant to weathering processes such as the presence of weak acids and oxygen. This weather resistance makes quartz much more durable in comparison to other minerals in sedimentary environments. Furthermore, quartz does not have cleavage and is very hard, which makes it resistant to mechanical erosion as well, thereby preserving its presence in sand dunes. The characteristics of quartz grains, which are sand-sized, rounded, and capable of being transported by wind due to their size and shape, contribute to their dominance in dune compositions.
Dune sand is usually uniform because heavier particles cannot be transported by the wind, leaving primarily lighter sand-sized particles, which are about 99% quartz. In addition to their resistance to weathering, these quartz grains are rounded, which aids in their transport by wind processes. Having rounded grains allows them to roll more easily, contributing to the accumulation in dune formations. The constant movement and sorting of sediment in the littoral zone or beach environment often result in well-sorted, homogeneous sand grains predominantly composed of quartz.
In different environments, such as humid areas and seashores, quartz grains tend to dominate because other minerals weather into clays, while in dry desert regions, a variety of minerals may be present, but there is typically less weathering to break them down. The uniformity and durability of quartz grains make them the primary constituent of many sand dunes around the world.
