Sand rose or desert flower One of nature’s rarest and most beautiful geological formations, a natural crystal structure that forms in arid desert environments through the interaction of dissolved minerals in groundwater with sand grains—specifically calcium compounds. As the water evaporates, calcium sulfate gradually crystallizes into overlapping plate-like layers that take on a petal-like, rose-like shape. These formations typically appear in sandy or brown hues and vary in size from small pieces to structures reaching up to about one meter in diameter. They are found in several deserts around the world, including those in Saudi Arabia, Qatar, and North Africa.