The Crater Lake Deposit is a large, scandium- and REE-bearing alkali igneous intrusive complex. Carbonatite and alkaline intrusive complexes (as well as their weathering products) are the primary sources of REE. Apart from REE, these rock types can also host deposits of niobium, phosphate, titanium, vermiculite, barite, fluorite, copper, calcite, and zirconium. Although these types of deposits are found throughout the world, only six are currently being mined for REE: five carbonatites (Bayan Obo, Daluxiang, Maoniuping, and Weishan deposits in China, and the Mountain Pass deposit in the USA) and one peralkaline intrusion-related deposit.

The Crater Lake syenites are interpreted to be a late differentiate product of the Mistastin Batholith. The dominant exposed lithology is coarse- to medium-grained, massive syenite, which is mainly composed of perthitic K-feldspar and 1 to 10% by volume of interstitial ferromagnesian minerals (Petrella 2012). A magnetic and melanocratic unit, ferro-syenite, which commonly contains greater than 50% by volume of ferromagnesian minerals, occurs as large continuous to discontinuous subvertical and conical bodies, sills, narrow dikes and inclusions in the felsic syenites. Three large ferro-syenite bodies have been found on the property: TGZ, Boulder Lake and STG. Petrella (2012) interpreted the narrow ferro-syenite dikes as having formed by fractional crystallization of ferromagnesian minerals, leaving behind a residual magma that produced the felsic syenites.

At Crater Lake, scandium was enriched in the residual liquid of the parent Mistastin granite magma following extensive fractionation of feldspar, in which scandium is incompatible. This residual liquid became the Crater Lake quartz monzonite magma, which was enriched in scandium and iron. Fluorapatite, zircon, fayalite, and the cores of zoned hedenbergite crystals saturated in this magma chamber. Ring faults developed as a result of caldera collapse, and the magma and minerals were emplaced as a slurry into these faults. The ferro-syenite formed by in situ fractionation of unzoned hedenbergite crystals, magnetite and hastingsite, and their physical segregation with the previously crystallized minerals. The extremely high FeO/FeO+MgO content of the quartz monzonite liquid resulted in high partition coefficients for scandium in the hedenbergite and hastingsite, allowing scandium to be incorporated into these minerals at exceptionally high concentrations under magmatic conditions. The physical segregation of hedenbergite and hastingsite in ferro-syenite cumulate rocks through gravitational settling and/or flow differentiation spatially concentrated the Sc-bearing minerals within the intrusion, resulting in the first known scandium deposit hosted by syenite.

The REE mineralization is contained in small primary idiomorphic zircon and hydroxyapatite crystals (identified by XRD analysis). The latter locally form aggregates that were wholly or partly replaced by britholite-(Ce). Two types of hydroxyapatite and one type of britholite-(Ce) have been identified. The first type of hydroxyapatite is magmatic and occurs as euhedral to subhedral, unzoned, transparent crystals that do not show evidence of having been altered. This type of apatite is very frequently observed in the other rock types of the intrusion. The second type of hydroxyapatite also occurs as primary, magmatic crystals but is compositionally zoned, with its core similar in composition to unzoned hydroxyapatite 1. This indicates that hydroxyapatite 2 continued to crystallize after hydroxyapatite 1. Crystals of hydroxyapatite 2 are commonly replaced in their outer parts by britholite-(Ce). Both types of hydroxyapatite commonly occur as inclusions in pyroxene, amphibole and, less commonly, fayalite.

The mining method selected for the Crater Lake project is a conventional drill and blast mine operation with truck and shovel excavation and transport of blasted material.

Mine production to feed the processing plant will begin in Project Year 1 and will average 426,100 t of mineralized material per year until Year 24 and decrease to 351,539 t at year 25. The life of the mine is 25 years. Mineralized materials will come from the Starter Pit in Year 1 and Year 2, then from the Middle Pit from Year 2 to Year 9, and finally from the Ultimate Pit from Year 9 to Year 25.

It was assumed in this PEA that overburden removal and hard rock mining will be performed by the Owner. Other scenarios involving contractors were not contemplated for this study, but such scenarios should be investigated during future studies on this project.

The overburden material is mainly constituted of glacial till at variable thicknesses, ranging from 0 m to approximately 10 m in the pit area. No drill and blast activities are planned for the removal of overburden removal.

The ore and waste rock material will be drilled and blasted in 10 m benches, then loaded into rigid-frame haul trucks with hydraulic shovels and wheel loaders.

In-pit haul roads and ramps are designed with an overall width of 22.5 m on overburden and rock. All ramps and haul roads are designed for double-lane traffic, except for the last two benches in the pit bottom which are designed for single-lane traffic of 16.5 m width to increase ore recovery from the deepest benches. Haul traffic must be closely monitored for safe operations when mining the bottommost two benches.

For in-pit dual-lane traffic on rock, a minimum width of 3.5 times the width of the largest truck was designed. The overall width of a 47-t mining truck is 4.8 m (CAT 772) which results in a running surface of 16.8 m assuming an operating width multiplier of 3.5 for dual-lane traffic. The allowance for a ditch (1 m) and a berm (2.5 m) increases the total road width to 20.3 m. The overall ramp width was design at 22.5 m to account for more flexibility for ditches and in the event the final truck selection is larger.

For in-pit single-lane traffic on the rock, a minimum width of two times the width of the largest truck was used. The overall width of a 47-t mining truck is 4.8 m (CAT 772) in a running surface of 9.6 m. The allowance for a ditch (1 m) and a berm (2.5 m) increases the total road width to 13 m. The overall ramp width was design at 16.5 m to account for more flexibility for ditches and in the event the final truck selection is larger.

The final pit design was designed to allow for multiple ramp accesses to waste and ore. The highest level is at Z=575 at surface and the deepest level is at Z=380 at pit bottom, with a total pit depth of 195m. A dual-lane traffic ramp of 22.5 m width was designed from surface to elevation Z=400, then a single-lane traffic ramp of 16.5 m width was designed from elevation Z=400 to pit bottom. The main ramp at the pit exit serves the ore crusher in the north, the waste rock stockpile in the west and the overburden stockpile in the northwest. A maximum grade of 10% was considered for ramps in the pit design to optimize haul truck performance.

The waste rock stockpile is located on the West side of the pit. It has a capacity of 10.5 Mm³ and can handle the total waste rock requirements 18.8 M tonnes. The maximum height of the waste stockpile is at Z= 570, and the lowest level on the ground of the topography is at Z=502.

The waste overburden stockpile is located on the northwest side of the pit. It has a capacity of 1.2 Mm³ and can handle the total overburden requirements 2.4 M tonnes. The maximum height of the waste stockpile is at Z= 580, and the lowest level on the ground of the topography is at Z=527.

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The mineral processing and metallurgical development programs have shown that scandium can best be recovered using magnetic separation to produce a scandium rich mineral concentrate and by treating the concentrate through caustic leaching, hydrochloric acid leaching of the caustic residue and solvent extraction to produce a high-grade Scandium Oxide (Sc2O3) and a mixed REE product. The Sc2O3 will be processed together with alumina to produce Al-2%Sc master alloy in a direct electrolysis process similar to the Hall – Heroult electrolytic method used for the production of primary aluminum.

The process design has been split in two locations. The Beneficiation Plant for the production of Sc rich concentrate will be located at Crater Lake near the open pit mine located about 200 km NE of Schefferville, QC. The Sc/REE mineral concentrate produced at the mine site will be transported to the Hydrometallurgical Plant located in Sept-Îles, QC, for the production of mixed REE product, ........