The Timmins Talc-Magnesite deposit is a hydrothermally altered ultramafic rock composed, at its core, largely of talc and magnesite although, at its fringes, the content of calcium in the carbonate increases.

The deposit under consideration has long been viewed as a potential source of magnesite and talc. These minerals are found in a variety of deposit types throughout the world and have a variety of end uses.

The best known of the minerals directly and widely exploited for its magnesia content is magnesite (MgCO3), one of the calcite group of rhombohedral carbonates, which includes calcite (CaCO3), siderite (Fe2CO3) and rhodocrosite (MnCO3), among others.

Although the genesis of natural magnesite deposits can be complex, it is distinguished in nature in two distinct physical forms, namely crystalline, (with a wide range of visible crystal sizes) and cryptocrystalline, sometimes referred to as amorphous, where the crystal size is not detectable to the eye and will range from 1 to 10 micrometers. The two types not only differ in crystal structure but in the sizes of the deposits and modes of formations.

Large-scale talc deposits form when magnesium in magnesium-rich rocks reacts with hydrothermal silica in the final phases of regional or contact metamorphism. Most commonly, talc (Mg3Si4O10(OH2)) or steatite (the massive and fine grained form of talc) replaces serpentine in an ultramafic rock like peridotite, either completely or more likely forming an outer rind with zoning (typically granite (silica source), vermiculite, chlorite, actinolite, talc, talc-carbonate and unaltered serpentinite).

The deposit consists of either a single large magnesite-talc altered dunitic komatiite or a series of altered flows. It is hosted by basaltic or andesitic lavas, serpentinized peridotitic komatiite and quartz-carbonate iron formation. It is about 1,800 m long, has a maximum width of 300 m and has been drilled to a depth of 120 m.

The very low CaO content in the magnesite-talc body makes the carbonate mineralization a potential source of refractory magnesia. However, iron substitution in the magnesite lattice means that the iron cannot be removed by standard physical methods. The iron, therefore, limits the grade of magnesia concentrate or dead-burned refractory product.

Several occurrences of talc-magnesite are known to be present on the property, the largest of which is located to the south of the diabase dike and is referred to as the A Zone. This zone has been traced by surface trenching, mapping and drill hole information along a strike length of approximately 1,000 m, to depths of approximately 100 to 150 m and achieves widths of 200 m at surface. The information available to date suggests that the A Zone has a near vertical dip in an overall sense, although the north and south contacts can be seen to locally dip steeply to either the north or south. A second zone of magnesite mineralization is located to the north of the diabase dike, although its dimensions and extents are known only from a small number of drill holes that suggest a strike length on the order of 1,000 m, with widths measuring on the order of a few tens of metres. A third zone of mineralization is located in the southwestern portions of the claim holdings and is exposed in surface outcroppings, but the extents of this zone are not known in detail.

The core magnesite zone is a massive, coarse grained, over-printed and re-crystallized magnesite and lesser talc unit showing no visible relic original textures. Within surfacestripped zones the exposures show a well developed set of quartz-carbonate extensional veins and stockworks, with subvertical to steep south dipping linker veins that strike easterly and are sigmoidally curved, moderately dipping tension ladder structures. Drilling indicates that the “high-grade” magnesite zones are wider than when exposed on surface, and carry much less veining than anticipated.

The transition zone has been logged as a talc carbonate-chlorite zone. It is physically similar to the above described core magnesite zone, other than it tends to be darker in tone (medium grey) due to the presence of aphanitic to fine grained black chlorite and tends overall to be more bladed to foliated in texture. The zone may be richer in talc and has a strongly developed carbonate groundmass, but shows variable lesser amounts of magnesite in inverse proportion to developed ferro-dolomite.

The proposed mining method for the Timmins Talc-Magnesite project is open pit mining with truck haulage delivering to a process plant located approximately 1.5 km southwest of the deposit. The average life-of-mine waste to plant feed ratio is 1.28:1. Mining will be by drilling and blasting for the bedrock, with the overlying overburden not requiring blasting.

The deployment of a contractor fleet has been assumed to manage pit operations, run-of-mine stockpiling and crushing. The final bench height in the open pit was designed for 20 m, with operational benches advancing in 10-m lifts.

Contractor fleet will be deployed to manage pit operations and crushing. Unit mining rates were provided by a regional contractor reflecting a typical fleet of 5-yd3 excavators and wheel loaders, 50-t trucks, track dozers, water trucks, service trucks and portable crushing and grinding equipment. Drilling and blasting would also be contracted and articulated trucks would likely be rented to address the overburden stripping campaigns.

The process facilities have been designed to treat 500,000 t/y of talc-magnesite ore, mined at the Timmins Talc-Magnesite mine. The plant will operate continuously with 85% availability to exceed 310 days per year.

The production of talc and magnesium oxide will involve processing the ore through a series of crushing, grinding, flotation, leaching, evaporation, decomposition and sintering steps.

A contractor will be responsible for crushing, screening and stockpiling the ore. Reclaimed ore will be conveyed to a tertiary crusher, followed by a primary grinding mill to reduce the particle size. The ground ore will be treated in rougher and cleaner flotation circuits where talc will be recovered to the concentrate streams. Flotation tails will be pumped to separate leach circuits. Talc will be flash dried, micronized and stored in silos.

Magnesite and other minerals contained in the flotation tails will be dissolved in the leaching circuit. The impurities are to be precipitated from the solution and excess water evaporated. The purified and concentrated solution will flow by gravity into decomposition units where active magnesium oxide (MgO) will be produced. The magnesium oxide will be then briquetted and screened. The briquettes from the screen will be dead-burned in shaft kilns and the resulting product is stored in a bunker. The fines from the briquetter screen will be returned to the process.

The primary reagent used in the leaching circuits will be recovered and recycled back to the process.

Slurry is conditioned with a collector reagent in a conditioning tank prior to flotation. The slurry is pumped from the conditioning tank to the first of four rougher flotation cells.

Rougher tails are pumped to a rougher tails thickener. An anionic polyacrylamide flocculant is added to the thickener to improve the settling characteristics of the solids. The thickener underflow is pumped to an agitated rougher tails thickener underflow tank, while the thickener overflow is pumped to a flotation area reclaim water tank.

The thickener underflow is pumped from the thickener underflow tank to a rougher tails filter where dry cake is produced. The filter cake is discharged and conveyed to the first primary leach tank. The filtrate is pumped to a flotation area reclaim water tank.

The rougher concentrate is collected in a (rougher) launder, and pumped by a vertical froth pump to a high-intensity magnetic separator (HIMS) in the regrinding area. The HIMS concentrate is pumped to a magnetic sand vacuum filter. The HIMS tails are pumped to a classification cyclone cluster. The cyclone overflow is discharged to a regrind mill discharge pump box. The cyclone underflow, with plus 0.1-mm size material, flows by gravity to a regrind mill, an attritor, where it is polished to 0.1 mm. The polished material is discharged to the regrind mill discharge pump box and pumped to the first cleaner column.

Cleaner flotation is carried out in three stages, each with one flotation column, followed by three mechanical cells. The columns and the cells in each stage are installed in a step arrangement to allow for flow by gravity.

The concentrate from the first stage column overflows to the second stage column. The concentrate from the first stage cells is collected in a launder and pumped by a vertical froth pump to the second stage column. The tails from the first stage cells are pumped to the rougher tails thickener.

The concentrate from the second stage column overflows to the third stage column. The concentrate from the second stage cells is collected in a launder and pumped by a vertical froth pump to the third stage column. The tails from the second stage cells are pumped to the first stage column.

The concentrate from the third stage column overflows to the third stage launder. The concentrate from the third stage cells is collected in the launder and pumped by a vertical froth pump to the cleaner concentrate HIMS. The tails from the third stage cells are pumped to the second stage column. The magnetic separator concentrate is pumped to the magnetic sand vacuum filter. The magnetic separator tails are transferred by pump to an agitated filter feed tank.

The magnetic sand vacuum filter filters the magnetic concentrates from primary grinding, regrind, and cleaner flotation circuits. The filtrate is pumped to a flotation area reclaim water tank. The filter cake is discharged to a load out area beneath the filter for loader transport to the magnetic sand storage area.

The cleaner concentrate HIMS tails are discharged to an agitated filter feed tank from where they are is pumped to a cleaner concentrate pressure filter. The filtrate is pumped to the flotation area reclaim water tank.

The filter cake is conveyed via a belt conveyor to a talc flash dryer, where it is dried using hot gas. The talc powder is separated from the hot gas via a cyclone. The solids are then pneumatically conveyed to a storage silo. A bag house is provided to capture fine particles in the gas phase before it is vented to the atmosphere.

Cleaner concentrate talc from the silo is pneumatically conveyed to three hammer mills operating in parallel, where the particle size is reduced to 50% passing 7.5 microns. A portion of the hammer mill product is further reduced in size to 50% passing 2 microns using two fluid energy mills installed in parallel. The micronized product from the fluid energy mills is pneumatically conveyed to one of the talc product silos for storage.

The leach circuit consists of a two-stage leach. Each stage has four agitated tanks which are arranged in series and staggered in elevation to allow flow by gravity.

Filter cake from the rougher tails pressure filter is fed to the first primary leach tank where it is mixed with secondary leach thickener overflow and secondary leach pressure filter filtrate. Regenerated reagent is also added to this tank. The discharge from the last tank of primary leach stage is pumped to the primary leach thickener.

The thickener is covered and vented to the tank vent scrubber. Flocculant is added to the thickener. The thickener overflow is collected in a primary leach thickener overflow tank from where it is pumped to impurity precipitation circuit. The thickener underflow is pumped to an agitated filter feed tank which is covered and vented to the local scrubber. The slurry is pumped to a primary leach pressure filter to produce washed filter cake. The filter is vented to a scrubber. The solids are conveyed to the first secondary leach tank. The mother liquor and wash filtrate are pumped to the impurity precipitation circuit.

The feed to the first secondary leach tank consists of the primary leach pressure filter cake, secondary leach pressure filter wash water and the regenerated reagent. Discharge from the secondary leach tanks is pumped to the secondary leach thickener. The thickener is covered and vented to the tank vent scrubber. Flocculant is added to the thickener to improve solids settling characteristics. The thickener overflow is collected in a secondary leach thickener overflow tank and then pumped into the first primary leach tank.

The thickener underflow is pumped to an agitated tank which is covered and vented to the tank vent scrubber. The slurry is then pumped to a pressure filter where solution is removed producing a filter cake. The solids are discharged to a load out area beneath the filter for loader transport to the ferruginous sand storage area. The filtrate is pumped to the first primary leach tank.