McDowell Mountains, Arizona | An odd doughnut-shaped granite orbicule found in a granite batholith on the north side of the McDowell Mountains. This feature is within a few meters of a pegmatite with large crystals of milky quartz, feldspar and other accessory minerals. The concentric layering is thought to have formed along the margin of semi-solid granite adjacent to a fluid-rich zone. The granite orb was found by a group of volunteers and stewards with the McDowell Sonoran Conservancy during a research project of milky quartz veins in the McDowell Sonoran Preserve. | Photo by Jack McEnroe.
Photographer: Jack McEnroe
Photo Date: May 2014
