The area of the Minera Florida Property is underlain by Upper Cretaceous volcanic and bintrusive rocks. The volcanic rocks comprise porphyritic andesite, lithic and crystal tuff, and brecciated tuff. The andesite is dark green and contains phenocrysts of plagioclase, orthoclase, pyroxene, and amphiboles. The bulk of these rocks are also affected by a sequence of hydrothermal alteration, as follows:
• Pervasive propylitization.
• Epidotization, in the form of aggregates and veinlets of epidote.
• Silicification, gradually increasing in intensity close to mineralized veins.
• Sulphide alteration, commonly in the order of 1% pyrite of the rock.
• Magnetite alteration, generally in the order of 5% of the rock.

Gold mineralization in the mine is hosted by quartz veins and brecciated zones within various types of Upper Cretaceous pyroclastic rocks and flow rocks of andesitic composition. The variety of the host lithology indicates that the primary control of mineralization was the permeability (brecciation) of the host rocks, followed by subsequent hydrothermal alteration and mineralization. In this respect, the more fragmental (and friable?) rocks are readily altered and contain gold mineralization, such as siliceous crystal tuff, lithic and crystal tuff, brecciated tuff, and porphyritic andesite.

The underground mining methods are sublevel open stoping and cut and fill. Access to the underground workings is from a number of adits, ramps, crosscuts, and drifts.

Trackless mining equipment is used exclusively underground. The ground is very competent, requiring little ground support in waste development, and minor rock bolting and meshing in ore development headings. The mine operates three, 8-hour shifts per day, and seven days per week. Ore is hauled using 25-tonne haul trucks via adits to surface haul roads, which wind their way down off of the steep topography to a transfer point.

The crushed ore is fed to two 3.7 m x 4.3 m ball mills where it is ground to a 65% passing 75 µm in closed circuit with a cyclone cluster. The cyclone overflow is then delivered to the flotation circuit that consists of eight 20 m3 flotation cells arranged in a rougher, scavenger, cleaner, and recleaner configuration. The bulk sulphide concentrate produced contains 22% Zn, approximately 105 g/t Au, and some silver (silver content varies with the head grade). The flotation plant recovers approximately 87% of the gold, 83% of the silver, and 80% of the zinc. The flotation plant tailings are pumped to the tailings facility.

The flotation bulk concentrate is thickened to 50% solids and leached with NaCN (sodium cyanide) solution in a series of ten 50 m3 leach tanks providing 72 hours of residence time. The products of the leaching circuit are a pregnant solution containing approximately 30 g/m3 Au and a thickened pulp containing the zinc sulphides. The leaching circuit recovers approximately 97% of the gold and 81% of the silver.

The pregnant solution is clarified, heated, and then pumped to four electrowinning (EW) cells where gold and silver sludge is deposited on the cathodes. The sludge is periodically washed off, filtered, and dried prior to being smelted into doré metal in a furnace. The doré metal is cast into bars containing Au, Ag, and approximately 5% impurities (Cu, Pb, Zn). The EW circuit recovers approximately 98.5% of the gold and 99.5% of the silver.

After electrowinning, the barren solution is used to heat the incoming pregnant solution via the heat exchanger and is then sent to an INCO SO2/air cyanide destruction circuit. The water from the INCO circuit is reclaimed as process water and cyanide is precipitated as stable cyanate and iron-cyanide salts that are disposed of in an impoundment area.

The thickener underflow containing the leached solids is filtered and stockpiled. The filtered solids are fed to the zinc flotation circuit at a rate of 3,000 tonnes per month (120 tpd). The zinc flotation circuit consists of ten 1.4 m3 mechanical flotation cells as roughers and scavengers followed by a 2 m diameter by 10 m high column cleaner cell. The final zinc concentrate contains approximately 56% to 60% Zn and the circuit recovers 70% to 77% of the zinc.