The Golden Sunlight veins are in a north-trending vein zone on the east side of the mountain, near a basin-margin fault of similar trend. Numerous small latite porphyry bodies in and near the Golden Sunlight mine are hydrothermally altered and mineralized and are the host for about 25 percent of the disseminated ore. About half of the ore body is in a breccia pipe that consists partly of fragmented argillite and partly of fragmented latite porphyry.

Quartz veins in north-trending zone cutting argillite and calcareous argillite of the Proterozoic Greyson Formation and latite of probably Late Cretaceous age. Veins are associated with a breccia pipe that hosts part of a large disseminated gold deposit. Gold is mostly free and associated with pyrite.

The 2BUG (Stage 2B, underground) mine began development in June 2015. This development consisted of accessing the remaining portions of the underground stages 1 and 2 and rehabbing the majority of the accessible workings. As well, two additional portals and a 295-inch bored raise were established and adjoined to the old workings, providing ventilation and secondary escape.

Originally, the 2BUG was intended to supplement the ore supply from the Mineral Hill, North Area and South Area open pits. However, due to geotechnical constraints with the Mineral Hill open pit west highwall and declining precious metal prices, surface mining operations were halted in November of 2015. This left the underground as a
standalone operation with the objective to recover the highergrade portions of the Mineral Hill breccia left behind by the idled pit.

The 2BUG, has implemented vein mining as well as sub-level longhole open stoping for recovering underground ore.

Golden Sunlight estimates it will open a new tunnel — the Apex. It can continue the life of the mining beyond 2021. That underground gold mine won’t connect to 2Bug. It will be above the water table and is just north of the current operation.

The ore treatment plant uses conventional carbon-in-pulp technology as well as Sand Tailing Retreatment (STR), designed to recover gold that would otherwise be lost in the process.

Gold is extracted from ore at GSM using a variety of physical and chemical processes. Ore is first crushed and ground, then gold is extracted using an agitated leach cyanide process.

Initial processing includes a crushing circuit consisting of primary, secondary, and tertiary crushing.

Crushing involves reducing rock particle size using gyratory and cone crushers to minus ¾ inch. Wet grinding in rod and ball mills further reduces rock size to 65 percent passing 100 mesh (150 microns or ~ 0.0058 inch). Grind circuit product is thickened with thickener and overflow is pumped to Carbon Columns where gold is adsorbed onto carbon.

Ground ore slurry is mixed with sodium cyanide, lime, and compressed air in eleven 400,000 gallon leach tanks equipped with agitators to keep the solids in suspension. The leaching process places gold into solution as a gold cyanide compound. Hydrocyclones separate the slime and sand fractions of the leach tailing in the wash circuit. The sand fraction goes to the Sand Tailing Retreatment (STR) circuit.

The STR circuit separates the gold bearing sulfides from the sand portion of the tailing by gravity concentration in spiral shaped launders. The pyrite rich concentrate is ground in a ball mill to 80 percent passing 400 mesh (37 microns or ~ 0.001 inch) to expose gold encapsulated in pyrite to further cyanide leaching. The ground slurry is subjected to a pyrite leach stage. Pyrite leach tailing is pumped back to the main leach circuit. The pyrite leach tailing product reports to the cyanide recovery and destruction circuit then to the tailing stream for disposal in the tailing impoundment.

The slime fraction from the washing circuit is sent to a thickener that produces two product streams consisting of a clear overflow stream and an underflow stream which contains all of the slime solids. Both streams are treated by carbon adsorption for gold recovery as the next step in the process. Carbon adsorption occurs in carbon in pulp tanks, and carbon columns charged with activated carbon made from burnt coconut shells. The carbon in pulp tailing product reports to the cyanide recovery and destruction circuit then to the tailing stream for disposal in the tailing impoundment.

The final processing step is removal of gold from the carbon in pressure stripping vessels. Gold removed from the carbon is returned to solution for electrowinning onto steel wool cathodes. The goldladen steel wool is smelted and poured into bars which assay about 75 percent gold, 8 percent silver, and 13 percent other metal impurities. GSM uses sloped floors, sumps, concrete barriers, and secondary and tertiary containment to contain solution within the plant site area.