Mineral Deposits Several small abandoned mine workings have been found within the park. One of these is a deep shaft along the south bank of the South Fork of Orestimba Creek, near the locked gate that marks the northeast boundary of the park. Samples from this shaft contain the mercury mineral, cinnabar. Other prospects consist of small tunnels in the Rooster Comb chert layer and to the north along the ridgetop east of Red Creek. These workings were in manganese deposits formed by hydrothermal alteration of the chert. Most recently, geologists of the U.S. Geological Survey and the California Division of Mines and Geology have found trace amounts of disseminated gold in the bleached zones associated with the Red Creek fault zone and related faults along Orestimba Creek.