Lake Lucero is a dry lakebed in the southwest corner of the park, at one of the lowest points in the basin. Rain and snowmelt from the surrounding mountains and upwelling from deep groundwater within the basin periodically fill Lake Lucero with water containing dissolved gypsum. When filled, the lake covers about at a depth of . As the water evaporates, small selenite crystals about in diameter form on the surface of the lake. Most of the crystal formation occurs when large floods concentrate the mineralized water every ten to fourteen years. Wind and water break down the crystals into progressively smaller particles until they are fine grains of white gypsum sand.
