The world's largest gypsum dunefield sprawls across New Mexico's Tularosa Basin — not sand at all, but pure white mineral crystals that remain cool even in desert heat.
Most desert sand is silicon dioxide — quartz. It heats to burning in the summer sun, turns brown and coarse, and blows in dense clouds that scour everything they touch. White Sands is made of something entirely different, and the difference changes everything.
Gypsum — calcium sulfate — is the mineral that forms when an ancient ocean or lake evaporates and leaves its dissolved minerals behind. Twelve thousand years ago, Lake Otero filled this basin. It evaporated. What it left was a vast deposit of selenite gypsum crystals, which weathering has broken down into fine white sand that covers 712 square kilometres.
Gypsum does not absorb heat the way quartz does. On the hottest days of summer, the sand remains cool to bare feet. It reflects light rather than hoarding it, creating a luminance that registers as uncomfortable to look at directly around midday. At dawn and dusk, the dunes turn pale pink and lavender, then gold.
Specific plants — yucca, skunkbush, cottonwood — have evolved bleached, white root systems and pale stems in synchrony with the dunes, staying anchored as the sand shifts beneath them. White lizards and white mice exist here and almost nowhere else, their albinism driven by thousands of years of predation pressure in a world where camouflage means survival.
The US military tests missile systems in the surrounding desert. Twice a week, the park closes for a few hours. The missiles fly. The dunes remain.