All sand is not the same. Sand is made up of a wide variety of elements that are not available in every location. The type of parent rock, size of granule, wear, position, organic content, age, temperature, and humidity are all factors that affect the properties of the sand. Each of these factors has an effect on the wear and shape of the grains of sand.
Sand types and conditions can vary in just a few miles and sometimes even from one side of the dune to the other. What is more the sand can change from day to day depending on the wind, rain and other factors. What was fine one day can be course the next if the wind carries away the fine grains and leaves the coarse remaining. Some elements in the sand will dissolve with water and my re-crystalize again in the sand itself. Volcanic activity, flooding and land slides will also change the sands composition. While sand is generally made up of silica it can be made of any element broken down small enough to be classified as sand. White Sands National Monument in New Mexico, USA is almost purely gypsum sand and looks like snow. Sand is one of the most diverse materials found on this planet and fascinating to study.
I hope this information will help you to understand what and why the sand is your first consideration. After all, sand is the main ingredient. With out it... there is no sandboarding.
If you would like more information on sandboarding and dune locations around the world be sure to stop by the location finder for details about that location.