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hiinera7ization in the Sunnyside Mine occurs in vein structures <br />P formed in vertical to near vertical faults and fissures associated <br />~ • with the Eureka graben structure. Target ore minerals related with <br />these vein structures include sphalerite, galena, chalcopyrite, and <br />I <br />native gold and silver. The gangue or host rock in which the tar- <br />~~ geted ores are found are comprised of quartz, manganese silicate„ <br />calcite, rhodochrosite, anhydrite, barite, and fluorite. <br />The mining method employed for extracting targeted ore is s'nrink <br />stoping, a mining technique which is normally used to mine steeply <br />i <br />dipping narrow veins such as encountered in the Sunnyside Mine. <br />i This mining method is basically an overhand stoping system in which <br />a fraction of the broken ore accumulates until the stope is completed <br />(see figure D-2). The increase in volume in broken ore as the stope <br />~ is developed requires that 30% to 50% be shrunk or removed from the <br />stope periodically through draw points to maintain an adequate working <br />• floor fer additional mining. Shrink stoping was selected as the <br />optimum method for ore extraction from the Sunnyside Cline based on <br />spatial characteristics of the mineral deposits, and mechanical <br />properties of the host rock. Upon removing targeted ore from the <br />place of deposition in the mine, the ore is transferred to the sur- <br />face of the American Tunnel portal by rail, and stockpiled for trans- <br />port to the mill facility. Waste rock produced in the course of mine <br />development is backfiiled into empty scopes or mixed with mine ore to <br />dilute mineral concentrations and enhance mineral recovery rates. <br />Water diversion and impoundment activities associated with <br />mine operations are discussed in Exhibit G. Briefly, underground <br />wo.-k,n9s occassionally intercept meteoric waters conducted try <br />• <br /> <br />2p,. <br />