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Cross Gold Mine <br />December 2024 U-5 <br /> <br /> <br />[1-5] Mill feedstock is crushed to approximately ½ inch and then ground [9] to an ultimate fineness of a <br />nominal 105-micron (140 mesh). The flotation process [11] treats the final grinding product. A nominal <br />mill feed capacity of 100 tons per day is the design target. <br /> <br />Coarse ore (pre-screened at six inches) is delivered to the crushing facility by front end loader and is <br />alternately deposited into one of two coarse ore bins [2] that can each hold 75 tons of six-inch material. <br />Coarse ore is withdrawn from the bins and delivered to a central belt conveyor which feeds a primary jaw <br />crusher. The jaw crusher reduces coarse ore to approximately 2 inches [3]. <br />The discharge from the jaw crusher is conveyed [4] to a double-deck vibrating screen for sizing. The <br />screen oversize is fed to a cone crusher [5]. The cone crusher operates in closed circuit with the screen. <br />Undersize (nominally minus ½ inch in size) from the screen is transferred via closed conveyor [6] to the <br />fine ore bin [7]. The fine ore bin is the entry point to the flotation portion of the mill facility. <br />The fine ore bin is being designed for a target of 250 tons of capacity. The crushing plant is intended to <br />be a day-shift-only operation but can be operated on a 24/7 basis if necessary. Subsequent mill unit <br />operations will be scheduled for three-shifts per day. Material is moved through the crushing circuit via <br />conveyor belt. <br /> <br />The grinding circuit consists of a ball mill [9] and associated classifier [10]. The ball mill feed belt is <br />variable speed and includes a belt scale. Soda ash is added to the ball mill feed belt to regulate the <br />alkalinity (pH) of the process water. Soda ash and other chemicals will be stored on the bottom floor of <br />the mill [19]. <br />Ball mill discharge is directed to the delivered to the classifier [10] where the ore particles of the desired <br />105-micron “fineness” are separated. The classifier returns the underflow (coarse material) to the ball mill <br />where it is combined with new mill feed. This ensures that all ore is ground to the appropriate size before <br />being pumped to the flotation cells. The grinding circuit underflow fines are discharged to the froth flotation <br />circuit [11] for the next precious metals recovery step. <br /> <br />In the flotation process, underflow from the grinding circuit is pumped to the conditioning tank where <br />several reagents are intensely mixed into the mineral-bearing slurry. The reagents include soda ash for <br />pH adjustment; active reagents (promotors and collectors) that adhere to the desirable metals; or <br />depressants to de-activate unwanted minerals. Conditioned ore is then diluted with process water and <br />pumped to the flotation circuit [11]. <br />The flotation circuit consists of typical froth flotation cells that are arranged in what is called a rougher- <br />cleaner-scavenger configuration. The flotation cells are supplied with air through an external blower. The <br />air creates a froth: activated minerals adhere to the bubble surfaces while waste minerals remain de- <br />activated and do not adhere to the bubble surfaces. The metal-laden froth is skimmed from the top of the