Crater Lake Project

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Mine TypeOpen Pit
StagePreliminary Economic Assessment
  • Scandium
  • REE
  • Total Rare Earth Oxides
Mining Method
  • Truck & Shovel / Loader
Mine Life... Lock
SnapshotOctober 24, 2023 – Imperial Mining Group Ltd. is pleased to announce that it has started work on the optimization of its mineral processing and hydrometallurgical flowsheet for scandium and rare earths, at SGS Lakefield, to support the preparation of a Prefeasibility Study of the Crater Lake Project in northeastern Québec. The work is supported by a $500,000 grant from Le Consortium de recherche et d’innovation en transformation métallique (CRITM), which is one of the nine industrial research sector groups in Québec. CRITM is funded by the Ministère des Ressources Naturelles du Québec.


Imperial Mining Group Ltd. 100 % Indirect
The Project is wholly owned by Imperial.

Deposit type

  • Intrusion related


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.



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Mining Methods


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CommodityProductUnitsAvg. Annual
REE Hydroxide t 1,865
Sc2O3 Al-2%Sc Master Alloy t 2,562

Operational metrics

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* According to 2022 study.

Production Costs

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* According to 2022 study / presentation.

Operating Costs

OP mining costs ($/t mined) CAD 7.8 *  
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* According to 2022 study.

Project Costs

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Mine Management

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