15/02/2024
On a clear day the west face of the Mazatzal Mountains’ Four Peaks dominates the horizon 45-miles east-northeast of Phoenix. Browns Peak is the tallest of the Four Peaks at 7,657 feet. The Peaks reside in the Four Peaks Wilderness of the Tonto National Forest. Rocks of the Peaks include a cap of early Proterozoic quartzite (Xql) resting on early Proterozoic meta-sedimentary rocks - Xsl (e.g., phyllite, psammite, and sparse quartzite). The cross section by Skotnicki illustrates the stratigraphic relationships and the presence of an overturned syncline.
The Four Peaks Mine situated near the south end of the Four Peaks is a world class producer of gem-quality amethyst, a species of crystalline quartz.
Citation: Skotnicki, S.J., 2000, Geologic Map of the Four Peaks 7.5' Quadrangle, Maricopa and Gila Counties, Arizona. Arizona Geological Survey OFR-00-11, map scale 1:24,000, 35-p report. https://library.azgs.arizona.edu/item/AOFR-1552430911756-451
