Lake Lucero is a playa, or seasonal lake. Water only collects there during the rainy season, and the rest of the year is it dry. Even when the lake has water, it is only about 12 inches deep, so it is not a place you could go fishing, or swimming. As the water begins to evaporate, the gypsum that is in the water begins to form a crust on the lake bed. Some of the gypsum forms beautiful crystals called selenite.
Selenite crystals are very soft.
You can scratch them with your fingernail. They are so soft that it doesn't take very long before the wind and rain begin to break them apart into smaller and smaller and smaller pieces. Soon they become so small that the wind can pick them up and carry them for short distances. We can see that there are many things that help to build the gypsum dunes at White Sands National Monuments. The mountains supply the gypsum.