The Sunshine Mine mineral deposits are narrow, high-grade vein deposits, which characteristically strike east-west and dip steeply (average 65°) to the south. The combination of faults, folds, fractures, and favorable host rocks created suitable conditions for mineral emplacement by silver-rich and silver-base metal veins.

The Sunshine Mine is one of the most productive mines in the more than 35 km long Coeur d’Alene Mining District. Mineralized deposits are localized in the 183 m thick St. Regis Formation and the underlying upper members of the 914 m thick Revett Formation. The contact between the formations is indistinct and locally picked as the bottom of the lower-most distinct purple-colored interval in the St. Regis. Rock types include argillite, siltite, sericitic quartzite, and vitreous quartzite. Siltite and argillite dominate in the St. Regis Formation; while in the Revett, lithologies are gray to pale greenish-gray siltite and quartzite. Changes in lithologies are noted on the scale from a few centimeters to a few meters. Detailed stratigraphy of the mine is poorly understood; geologic mapping by early workers focused on veins and alteration, facies changes, and subtleties between lithologies that complicate correlation and identification of rock units. The stratigraphic column in the mine is continually re-interpreted, and two apparent marker beds have been identified in the West Chance area. One of these argillaceous beds is thought to be a bentonite ( ........

Production mining has been broken into three mining areas. The three mining areas are identified as the Upper Country (above 2300 Level), the Lower Country (below the 2300 Level and above the 4600 Level), and the Bottom Area (below the 4600 Level and above the 5800 Level). The Bottom Area includes 23 stopes on the 4600 Level that were initially omitted from the Lower Country area.

Most of the mineralized material is planned to be hauled to the Jewell Shaft mineralized material loading pockets and hoisted to the surface up the Jewell Shaft. The exception will be material above the 2300 Level, most of which is planned to be hauled up the upper mine ramp system to the surface. Waste material will either be used as backfill or hauled to the Silver Summit Shaft. Some waste may also be hoisted by the Jewell Shaft.

The Jewell Shaft and hoist is planned to be rehabilitated and equipped with new lighter bottom dump skips, raising the hoisting capacity to 1,179 tpd. The mineralized material is planned to be unloaded into the concentrator’s coarse mineralized material bin, while the first 453,600 tonnes of waste is planned to be placed in the existing WRSF and the remaining waste will be hauled to the ConSil WRSF or hoisted up the Silver Summit Shaft and hauled to the nearby ConSil WRSF. Some waste can be used as backfill in longhole and overhand stopes.

Potential mining methods include underhand and overhand cut and fill mining generally using paste ........

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