The main attraction of any White Sand National Park tour is going to be the sand itself. The iconic white dunes that cover the park are actually made of tiny particles of gypsum, not silica like most inland sand. Unlike silica, gypsum sand is naturally clear, but as the particles rub and bump up against one another, they develop scratches that reflect the sun’s rays.

Those reflective scratches make the sand at White Sand National Park appear completely white, almost like snow. Because gypsum sand is so rare and difficult to preserve, White Sand National Park is the only place in the world where you can see these unique, bright white dunes.

The reason why gypsum sand is so hard to find is that it’s much more soluble than most other minerals. While silica sand dunes can survive the rain, gypsum dissolves in water and is usually washed away. So why is there such a large concentration of gypsum sand at White Sand National Park, and why doesn’t it just wash away when the rain comes?

The answer is that the park is surrounded by mountains and is entirely closed off from the outside world. When the rain does fall (a relatively rare occurrence in New Mexico), all the gypsum sand dissolves in the water but doesn’t go anywhere. When the rainfall evaporates, the sand is left behind.

Here’s another fun fact about gypsum dunes: Unlike silica, gypsum doesn’t absorb heat from the sun. That means that, even in the summer heat, the sand dunes at White Sand National Park are cool to the touch—you can even walk on them barefoot without burning your feet.

To make the most of your trip to New Mexico, check out our White Sands National Park Self-Guided Driving Tour, or you can sign up for Action+ and gain access to over 100 tours for a single yearly price.