The Copperstone deposit is a mid-Tertiary, detachment fault related gold deposit. Mineralization is predominantly controlled by the northwest trending shallow angle Copperstone fault and shear zone. These structures are not confined to any lithologic unit, although the majority of the mineralization is hosted in quartz latite porphyry. Breccia textures as well as chloritization, silicification, and hematite and specularite flooding are reliable indications of gold mineralization.

The Copperstone deposit is presently best described as a mid-Tertiary, detachment-fault related gold deposit. Detachment faults are low-angle (up to 30°) normal faults of regional extent that have accommodated significant regional extension by upward movement of the foot-wall (lower-plate) producing horizontal displacements on the order of tens of kilometers. Common features of these faults are supracrustal rocks in the upper-plate on top of lower-plate rocks that were once at middle and lower crustal depths, mylonitization in lower plate rocks that are cut by the brittle detachment fault, and listric and planar normal faults bounding half-graben basins in the upper plate (Davis and Lister, 1988).

Salem (1993) suggests that the Copperstone deposit might be further classified as a new sub-set of volcanic-hosted epithermal precious-metal deposits, postulating that Copperstone was created during a late stage of detachment faulting, and that localization of gold deposition was cont ........

The Copperstone Mine had historic open pit production from 1987 through 1993 by Cyprus and in 2012 American Bonanza Gold Corp started underground mining from two declines which were developed in the bottom of the open pit. American Bonanza’s mining focused on the D zone, which is to the north of the open pit, and mined 163,000 t of ore form January 2012 to July 2013. Due to the historic underground mining that has taken place on the property and the exploration drift developed by Kerr in the summer of 2017 there is a currently 12,800 ft of access development. This existing access includes two declines from the bottom of the pit and extends across 500 ft of strike. Therefore, a reduced amount of development is required to get the mine up to full production. The PFS mine plan for the Coppertone Project includes approximately 884,100 tons of mineral reserves to be extracted by underground mining in 4.4 years. The mine production schedule calls for the production of 600 tpd of ore seven days per week and 840 tpd of ore processed per mill working day, 5 days per week. Mining recoveries of 95% were applied and overall dilution factors averaged 25.3%. Dilution factors are calculated based on internal stope dilution calculations and external dilution factors of 10%. The ore will be placed on a stockpile at the mill and a loader will be employed to feed the mill at three eight-hour shifts, five days per week.

The mine plan for the reserves is based on the following criteria ........

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