These images show a magnified view of sand particles. Although sand looks quite similar in many different places across the world, it has unique characteristics. The size and size distribution of the particles vary significantly between different kinds of sand. The angularity of the particles also changes drastically. Sand that has been moved across a river is usually rounder, due to the mechanical abrasion of water and other surrounding sediments. This sand is mostly made of quartz and feldspar. Quartz is the white or transparent phase of the mineral. Feldspar, on the other hand, is pink colored. Identifying these minerals is not an easy task. Darker areas could potentially be olivine or hornblende. These phases are more difficult to identify for people who are not trained in geology or earth science.