There is no known formal industrial mineral ore deposit model for alunite. The characteristics for a model and some exploration criteria are derived from three publications: Hall (1978), Hall and Bauer (1983), and Hofstra (1984).

The local alunite deposit has been described, in the above-mentioned publications, as hydrothermal alteration of calc-alkaline volcanic rocks.

Alunite mineralization is found on four ridges that occur within the Blawn Mountain Project. Acid sulfate alteration associated with a shallow, possibly laccolithic intrusion altered the silicic-alkalic rhyolite porphyries, flows and tuffs belonging to the Miocene Blawn Formation and the Oligocene Needles Range Group. Alteration tends to be in linear bodies reflecting the role of normal faults in controlling the mineralization. Alteration is zoned away from the point of hydrothermal fluid upwelling. The mineralized ridges are erosional remnants of a once larger altered area.

Krahulec (2007) described the appearance of rocks from the silica cap and quartz-alunite zone as follows, “The Silica Cap is a zone of intense silicification believed to be the near-surface manifestation of the hydrothermal channel-ways. The silica is typically buff, dense, and massive but may be quite porous and vuggy locally and resemble a siliceous sinter… On the surface the Quartz-Alunite alteration zones are composed of white to cream to buff to gray to pink, generally fine grained, punky to dense, intermixed alunite and silica with only minor amounts of other impurities, mainly iron… Alunite also occurs locally as coarse (>0.5in.), lathy, typically pink crystals in veins. Kaolinite becomes increasingly important, at the expense of alunite, in the Quartz-Alunite zone near the boundary with the Hematite-Clay zones and also where the QuartzAlunite zones are cut by faults (Walker, 1972). Dickite (a high-temperature member of the kaolinite group) is reported by Whelan (1965) and Thompson (1991) in the Quartz-Alunite zone”.

Krahulec gives the following description of the two geometries, “The cone-shaped (narrow end at the base) zones are interpreted as the primary area of strong hydrothermal upwelling . . . and the adjoining flat-bottomed zones are recognized as permeability-controlled areas above the paleoground-water table where steam-heated H2S is oxidized to H2SO4. Only the central portion of Area C (Area 1) at Blawn Mountain is clearly a funnel-shaped zone. The other flat bottomed alunite zones are strongly controlled by the higher porosity and permeability of the host volcanic rocks, while the hydrothermal cones are largely independent of these factors (Hofstra, 1984)”. Krahulec continues this discussion by quoting Hofstra, “…The control of permeability on the degree of alteration intensity is most important near the margins of Quartz-Alunite altered zones. Alteration is pervasive and unaffected by variations in the permeability of the host rocks”. The alteration zones tend to be thicker in cone-shaped areas than in flat-lying areas. It is possible that there were more cone-shaped feeder zones but they were eroded or are buried under valley fill.

Mining operations will use a conventional open-pit, truck and shovel mining approach. This is a typical and standard approach for many surface mining applications and takes advantage of the flexibility of the mining equipment. For Blawn Mountain, Area 1 and Area 2 will be developed in phases that will allow for optimizing the ore grades encountered in the deposit, while providing flexibility to the operation.

The mining plan for the PFS uses a nominal 3.75% K2O ore grade cut-off for Area 1 and a 3.50% K2O cut-off for Area 2. These cut-off grades were utilized in the development of the pit shells and mining areas for Area 1 and 2. In addition, two low-grade ore stockpiles will be developed, one for Area 1 and Area 2 respectively. Ore that is less than 2.75% K2O is considered waste material and will be placed in the waste dumps. The Area 1 low-grade stockpile will contain ore ranging in grade from 2.75% K2O to 3.75% K2O and the ore in the Area 2 low-grade stockpile will range from 2.75% K2O to 3.50% K2O. This low-grade ore will be fed to the processing plant after mine operations have concluded in year 28.

The mining production schedule is driven by the capacity of the processing plant. The ROM ore production schedule for direct plant feed is approximately 3.4Mtpy.

Primary Crushing
The ROM ore at minus 12in is delivered to the 400t dual loading hopper that feeds two parallel primary roll crushers, one operational and one stand by. Each roll crusher with a capacity of 425tph will crush the ROM ore to minus 3in.

The crushers are sized to operate 7,920 hours/year. The crushed ore will be conveyed to a collection bin which will feed two parallel screening/secondary crushing units.

Secondary Crushing
The collection bin will feed two dry crushing screens. Screen oversize will report to two secondary cage mills. The crushed product from the cage mills will be recycled back to the dry screens via bucket elevators. Screen undersize (P80 – 1mm) will be conveyed to the calciner feed bin. A dust collection system will be installed to manage the dust generated from dry crushing.

The ROM ore will be processed as envisioned, by crushing, reduction roasting, extracting SOP by leaching the calcine with water, solid/liquid separation, evaporation of brine, crystallization as well as drying and packaging of SOP product for markets. Provisions have been made in the process plant to conserve energy and water through treatment and reuse of effluents and disposal of residues in an environmentally sound manner.

Crushed ore containing alunite and inert solids at approximately 98% solids (2% moisture) is
dehydroxylated and roasted to decompose the alunite. The calcine produced contains a mixture
of SOP (K2SO4) and alumina (Al2O3). A start-up air heater is used during the system start-up to bring the flash roaster up to the auto-ignition temperature of the fuel.

The calcine produced from the roasting step is quenched with water and the slurry is pumped to the water leach circuit. Calcine particles entrained in the roaster off-gases are se ........