Based on current published explanations for the Mineral Ridge mineralization, it appears that a structurally-controlled orogenic model may be the most applicable to the deposit.

Much of the known mineralization has been mined out in the Drinkwater, Mary LC, Wedge A, B, C, and D, Bluelite, Solberry, Missouri, Brodie, and underground portion of the Oromonte areas.

Five areas of remnant mineralization adjacent to the Drinkwater, Mary LC, Bunkhouse Hill, and Brodie open pits are considered to remain prospective for remnant open pit mining, as is the Custer area, which has no open pit mining history, situated to the southeast of Bunkhouse Hill. Four of these areas are on the eastern, Drinkwater, side of the Mineral Ridge antiform (Drinkwater, Mary LC, Bunkhouse Hill, Custer), and two, Oromonte and Brodie, are on the western limb of the antiform.

The currently-known mineralized zones occur over an area of approximately 14,000 ft (4,300 m) north–south and 15,000 ft (4,600 m) east–west.

The gold mineralization at Mineral Ridge is primarily associated with milky quartz veins and lenses accompanied by local argillization and some sericitization. Prior to mining, the individual zones were as much as 50 ft (15 m) thick, typically consisting of a higher-grade quartz veins from five to 30 ft (9 m) thick, surrounded by a lower-grade envelope of mineralization. Two or more high grade zones are commonly observed stacked in en echelon patterns.

Gold deposition is structurally-controlled, and some of the highest-grade mineralization is found in shoots that are at an oblique angle to the direction of movement of extension.

Gold is present as native gold and electrum that occurs as irregular shaped intergrowths in quartz associated with interstitial space and small fractures. Gold also occurs as irregularly shaped intergrowths and as fracture fillings associated with goethite, much of which was derived from original pyrite. In partially oxidized mineralization, gold occurs with both pyrite and goethite. Locally, minor amounts of galena, graphitic to carbonaceous material, sphalerite and anglesite/cerrusite have been observed, with galena and graphite appearing to be associated with higher-grade gold values.

Gold particle size varies from 1 to 2 µm to about 700 µm, but most of the particles are in the 5 to 50 µm size range. Gold to silver ratios are typically in the 2:1 range.

There are two elements to the proposed mining methods for this study. The first area involves the mining of the previously-processed heap leach material and processing it though a milling facility. The second item involves the mining of remnant areas adjacent to existing open pits on the property and sending this material to the new process facility. The milling facility will have a higher gold recovery than the heap leach process, so the remnant areas have become economic to mine.

Production of mineralized material from the heap and pit area is planned at a nominal rate of 4,000 t/d. Due to the timing of building a new pad storage area for the heap leach material, the heap leach material has to be processed before the mining of the pit areas to allow room for the additional material from the open pits. Mining and processing of the heap ore will take a little over five years and mining and processing of the open pit ores will take three years for a total projected mine life of 7.5 years.

LEACH PAD
Mill feed material is derived from moving the previously-processed heap leach material from the existing heap leach to a mill facility, to process and reclaim economic material from the leach material.

No drilling or blasting is anticipated as the reclaim leach material is unconsolidated. All material movement will consist of transporting the reclaim leach material from the existing heap leach pad to the mill facility. A hopper and solution mixing system will be constructed on the leach pad in order to pump material directly from the leach pad to the mill. After materials are processed through the milling operation, the tailings leaving the mill will be placed back on the pad using conveyor stackers.

To convey the reclaim material from the pad to the mill, the material will be mixed into a slurry using a mixing system constructed on the pad. The mixing system will comprise a hopper, a mixing tank, pumps and piping. To remove ore from the pad, a 10 yd3 front-end loader (CAT 988K or equivalent) will load reclaim leach material into the hopper. Reclaim material within close proximity to the hopper/conveyor system will be pushed with a dozer (CAT D8T or equivalent) such that the front-end loader can load the material. A 50 yd3 scraper (CAT 637K or equivalent) will load and haul material that is located further away from the hopper and dump it near the hopper. Reclaim material will generally be removed from the top down, proceeding west to east and south to north.

REMNANT MATERIAL
The Mineral Ridge deposits contain mineralization at or near the bedrock surface that are ideal for open pit mining methods. The method of material transport at Scorpio Gold will be open pit mining using two to three 16-yd3 front-end-loaders as the main loading units; a 6.6-yd3 excavator will be used for sorting out narrow ore zones. The open pit mineralized material will be loaded into 100-t haul trucks and transported to the crushing site next to the mill. Waste material will be transported to a designated WRSF for each pit.

Mining is currently planned on 20 ft levels, but areas that contain ore zones are designed to be mined in approximately 10 ft levels. All blasting will be conducted per MSHA regulations on mines and mining plants. Blastholes 6.75 inches in diameter will be drilled on an approximate 13 ft x 14 ft staggered pattern for a 20 ft bench in the non-mineralized area. Blastholes 4.5 inches in diameter will be drilled in the mineralized zones on an approximate 10 ft x 11.5 ft staggered pattern on 10 ft. benches. All material will be blasted, generally using ANFO, with up to approximately 20% of the blasting requiring emulsion for better fragmentation and possible wet holes due to precipitation.

Pit Design.
Mineral Resources for the remnant areas were evaluated using a LG pit optimizer to generate optimized pit shells. Pit shells were generated based on varying metal prices with a base gold price of $1,300/oz. A total of 51 pit shells were generated to determine optimal break points in the pit phases and the final pit phase for each deposit. The Oromonte pit was designed in two phases, due to the large strip that would be required for this area. All other areas were designed in one pit phase, but the Custer, Mary LC and Drinkwater areas were designed with two different pits. The Custer pit has small satellite pit referred to as the South Custer pit, the Mary-LC pit has a small satellite pit referred to as the West Mary pit, and the Drinkwater pit has a small satellite pit referred to as the South Drinkwater pit.

Haul roads are designed at a width of 80 ft, which provides a safe truck width (21 ft wide for 100- ton vehicles) to running surface width ratio of 1:3.5. Maximum grade of the haul roads is 10%, except for the lower benches where the grade is increased to 12%, and the ramp width is narrowed to 60 ft to minimize excessive waste stripping.

The current Drinkwater pit has a high wall of an approximate 400 ft height which shows no significant signs of instability. The highwalls in the Drinkwater, Mary LC and Brodie pit have actual slope angles that range between 46–48º. Scorpio Gold uses a 48º inter ramp slope for internal designs. Based on the past studies and current highwall conditions the pit deigns for reporting the Mineral Reserves were completed at a 47º inter ramp slope, with 20 ft catch benches every 40 ft. This results in a bench face angle of 66.6º. The use of preshear drillholes along the highwall has been added to the mine plan so this will also help with preserving the highwall integrity.

The pit design criteria are:
Ramp Widths - 80 ft;
Ramp Grade - 10%;
Ramp Widths Pit Bottom - 60 ft;
Ramp Grade Pit Bottom - 12%;
Minimum Turning Radius - 120 ft;
Ore Mining Levels - 10 ft;
Waste Mining Levels - 20 ft.

Pit Slope Angles:
Safety Bench Spacing - 40 ft;
Inter-ramp Pit Slope Angle - 47°;
Bench Width - 20 ft;
Batter Angle - 66.6°.

The process plant is designed to process 4,000 t/d, equivalent to 1,460,000 t/a.

RECLAIM AND GRINDING AREA
The grinding plant will receive residual material from the heap leaching operation. This material will be reclaimed with a front loader at a feed rate of approximately 181 t/h. The reclaimed material will be fed to a reclaim mixing tank trough a vibrating grizzly that will remove previous heap leach operation trash. The mixing tank will be agitated and process water will be added to form slurry with approximate 55% solids. The slurry will then be pumped to a holding tank (21 ft by 21 ft) with a retention capacity of 60 minutes, and then pumped to the ball mill pump box. This material will have a top size of approximately 0.25 in and a passing 80% under 0.14 in.

The slurry will feed the ball mills pump box at a controlled rate. The ball mill pump box will have approximately 90 seconds of storage capacity. The current design contemplates two ball mills (12.5 ft by 25.5 ft) with a motor of 2,400 hp each. Both mills operate in parallel with a shared pump box for both mills and in closed circuit with a cyclone pack for each mill that will control the grinding circuit product size. Pumps with variable frequency drivers will pump slurry in the pump box to the hydrocyclone packs. Each hydrocyclone pack will have nine cyclones of 10 in diameter with an arrangement of seven operating, and two in standby. The hydrocyclone overflow has a design 80% passing size (P80) of 200 mesh and will be the final grinding circuit product that will be sent to the linear trash screen in the leaching area. The hydrocyclone underflow will feed the ball mills at a circulating load of 300% and a solids content of 77% w/w.

LEACHING AREA
From the grinding circuit, the hydrocyclone overflow material will flow by gravity to the trash linear screen, which will prevent any oversized trash from reporting to the CIL circuit and interfering with the interstage screens. The trash linear screen undersize will report by gravity to the pre-leach high-rate thickener (80 ft diameter). Flocculant will be added to aid the settling process. The underflow density of the thickener will be of approximately 60% solids. The thickener underflow will report to a pump box from which the slurry will then be pumped to the leaching circuit. The thickener overflow will be recycled to the process water pond for reuse.

There will be four leaching tanks (50 ft by 52 ft) operating in series with a total capacity of 353,160 ft3 (10,000 m3 ) that will provide a total leaching residence time of 36 hours. The leach feed density will be adjusted by recycling water from the water process pond to operate at 45% solids. Air will be injected into the tanks through spargers aiming to improve oxygen dissolution in slurry during the leaching of gold and silver. It is expected that the slurry will arrive at the CIL circuit at a pH of 10.5 and it will be adjusted as necessary to maintain high alkalinity. Sodium cyanide (NaCN) will be added to the first and third leaching tanks and its addition rate will be controlled based on cyanide analyses. Cyanide concentration in the slurry will be maintained at 0.03 to 0.06 lb/ft3 (0.5 to 1.0 g/l) sodium cyanide. The slurry will flow by gravity between the tanks. Each tank is equipped with twin impeller agitators to maintain its slurry solids in suspension, one interstage screen to prevent activated carbon from flowing co-current with the slurry, and one carbon advance pump for carbon movement counter-current with respect to the slurry flow.

After the leaching process, barren slurry from the final leaching tank will flow to a carbon safety screen, which will prevent the loss of carbon in the instance that the final inter- stage screen has become deficient. The safety screen undersize slurry will report to the CIL tailings thickener feed tank. At the tailings thickener (80 ft diameter high rate thickener), the leaching barren solution will be thickened to produce an underflow product of 55 to 60% w/w solids, to aid with filtration. The thickener underflow will be pumped to plate- and-frame filters pump box. The tailings thickener overflow will be recycled to the process water pond and utilized in the CIL circuit, as required to adjust solids densities.

Fresh or reactivated carbon will be added to the final tank after rinsing with fresh water in the carbon sizing screen. The designed activated carbon concentration in the leaching tanks is 0.94 lb/ft3 (15 g/l). The carbon will be moved counter–current to the slurry flow by recessed impeller centrifugal carbon transfer pumps. Dissolved gold and silver in the slurry will be adsorbed onto activated carbon and finally removed from the circuit at the first tank. The removed carbon will feed a loaded carbon screen that will capture loaded carbon in the oversize. Loaded carbon will be bagged and transported to an external facility for final gold and silver recovery, and carbon regeneration and recycling. The loaded carbon screen undersize will be returned to the CIL circuit.

The current operation at MRG is a heap-leach operation, which uses reactivated carbon to adsorb gold from the pregnant leach solution. Most of the existing infrastructure for receiving new carbon, attritioning, sizing, sampling, and shipping the loaded carbon to the external facility will be reusable in the new process.

The proposed process plant can be modified to treat ROM open pit material. The plant will treat ROM material up to a nominal rate of 4,000 t/d. A crushing facility already existing on the property will be modified to produce a final crushed transfer material to the grinding circuit of 0.39 in (10 mm) T80. In addition, an extra total power of 540 hp (270 hp each ball mill) will be necessary in the grinding circuit to accommodate the increase in the feed size from 0.14 to 0.39 in. The crushing plant will supply crushed material at a rate of 168 tph during one 12-h shift, the heap leach material will be processed during the other shift.

The crushing circuit will consist of a 32 x 48 jaw crusher (existing) with a close side setting (CSS) of 4” that will be fed by a feeder with a maximum rock size of 24 in, which is controlled through the existing grizzly. The jaw crusher product will feed a 400 hp secondary cone crusher with a CSS of 5/8 in (16 mm). The cone crusher will work on a close loop with a double deck screen (7/8 in and 5/8 in apertures) to produce a final product P80 of 3/8 in (10 mm). Final crushed product will be transported to the ball mills by a single belt conveyor, and then split to feed the two ball mills equally.

Besides the increment in power to the ball mills, all other main process equipment in the comminution and leaching circuits (cyclones, CIL tanks, thickeners, filters) will remain unchanged.

The loaded carbon will be shipped off-site to a refinery to recover the gold and silver.