"what kind of sand dune appears to be most common in this dune field"

The most common dune form on Earth and on Mars is the crescentic. Crescent-shaped mounds generally are wider than long. The slipface is on the dune's concave side. ... Some types of crescentic dunes move faster over desert surfaces than any other type of dune.

Explanation:

One positive impact of the mining is that the sale of the Bauxite will increase their economic power by bringing in foreign exchange into their economy. This will improve services such as healthcare and infrastructure.

A negative impact is the destruction of the nature preserve and disturbing the ecosystem could lead to a devastating loss in biodiversity. A decrease in biodiversity will increase crop pests and diseases that destroy standing crops, and an increase in the prevalence of diseases in the community.