Wide alluvial plains in southwest New Mexico are a feature of the basin and range province, with isolated fault block mountains scattered like islands from a sandy sea. Volcanic rocks form most of the Cedar Mountains to the south and the Pyramid Mountains to the west, but the Burro Mountains to the northwest are mainly ancient granites at an elevation of 4,560 feet. The yucca is a member of the lily family with pearly white spring blossoms. Early Indians used its tender shoots for food, made soap from its roots, and made sandals and basketry from the leaf fiber. A single variety of moth produces pollination.