Iron-oxide concretions – curious-looking dark spheres – can be found by the hundreds of thousands in the dramatic red and white outcrops of Navajo Sandstone in Utah. The concretions typically consist of a sandstone core surrounded by a thick iron-rich rind, and they have an interesting geologic history and Native American cultural history. They also resemble Martian spherules or "blueberries", and may share similar origins.
Grand Canyon, Zion, Arches, Canyonlands, and other national parks on the Colorado Plateau encompass some of the most spectacular scenery on Earth. Extending across the Four Corners region where the borders of Utah, Colorado, New Mexico, and Arizona meet...the landscape is sculpted into dramatic cliffs and arches, domes and towers, fins and hoodoos, mesas and buttes, slot canyons, and deeply carved canyons.