Petrographic and scanning electron microscopy (SEM) analyses of quartz grains from beach and dune sands were carried out in the western and eastern Northland coasts, New Zealand, to examine variations in durability and surface texture, which are controlled by mechanical and chemical processes, in profiles across beach and dune environments. This was done through point counts of quartz grain properties based on extinction angle and crystallinity. Variations in surface texture were assessed through SEM observations of mechanical features (conchoidal fractures, smooth surfaces, groove forms) and chemical features (solution pits, etching, silica deposits). Mechanically produced grooves are associated with beach sands affected by the high energy of the surf zone. Both mechanical and chemical processes occur in the eastern dune sands. They are associated with the greater abundance of angular grains in the eastern dune sands than the western dune sands. In addition, conchoidal fractures produced by the collision of grains in aeolian environments and linear and curved grooves produced by quartz grains from the beach support the mechanical processes taking place in the dunes. Solution pits, etching, and the presence of diatoms in the quartz grains are associated with pedogenesis and high silica precipitation in the eastern beach and dune sands. The durability of coarse-grained polycrystalline quartz relative to fine-grained polycrystalline quartz suggests that chemical abrasion exerts control over the distribution of quartz types in the dune sands.

Grain size determinations were carried out for 54 beach-sand samples from the western (n = 25) and eastern (n = 29) coasts of the Gulf of California, Mexico, in order to establish the relationship among coastal processes, relief, and grain size parameters for both areas based on grain size distributions. This was done because both coastal areas are controlled by marine processes and the geomorphology of the coast, since fluvial discharges are negligible in the distribution of sands. In general, sands from the western coast are mainly coarse, moderately sorted, near-symmetrical with leptokurtic and very leptokurtic distributions. Correlations between grain-size parameters for the western coast are controlled by less selectivity in the coastal processes to concentrate fractions in a specific range of sizes, a narrow coastal plain, and compositional differences in the sands due to the heterogeneous lithology and the presence of carbonate shells. Eastern coast beach sands are medium, moderately well sorted, near-symmetrical with mesokurtic to leptokurtic distributions. Correlations between grain size parameters for the eastern coast are controlled by longshore current drifts in a northwestern direction and a wider coastal plain compared to the western coast.

A scanning electron microscopy analysis was performed for 570 quartz grains from desert and coastal dune sands in NW Mexico. Our main goal is to present a new application in the use of ternary diagrams with logistic normal confidence region boundaries of normalized data based on quartz surface textures (i.e., constrained data) of desert and coastal dune sands. This was done to demonstrate that quartz surface textures from desert and coastal dune sands are not significantly different even though there are apparent dominant processes (mechanical, chemical) that produce different surface textures in quartz grains from both dune types. This may be associated with the fact that quartz grains deposited in the dune sands do not reflect a second cycle of transport associated with an aeolian environment because of their low textural maturity, provenance, closeness to the source rock, and little attrition process. This study indicates that quartz grains from the desert dunes display mechanical textures probably associated with the Colorado River Delta and granitic sources that do not reflect accurately the aeolian mechanisms controlling the transport of these grains. Also, some quartz grains display chemical surface textures probably linked to the hydrothermal activity near the Colorado River Delta. In general, quartz grains display conspicuous surface textures. Quartz from coastal dune sands displays chemical surface textures that indicate quartz precipitation from silica-saturated water and, to a lesser extent, it displays mechanical features. These similarities might be associated with the mixing of processes (mechanical, chemical ) in quartz from the desert and coastal dune sands.