Work carried out to date indicates that the Maracás vanadium-rich titaniferous magnetite deposit is situated in a geologic environment similar to other magmatic vanadium-rich magnetite deposits. The Rio Jacaré intrusion that hosts the deposit is a mafic to ultramafic layered intrusion characterized by both rhythmic and cryptic layering that includes a pyroxenite/gabbro layer in the upper part. This gabbro layer hosts the Campbell vanadium deposit. The deposit has been assigned this way by the manner in which it was generated as an early magmatic ore type deposit formed by concentration through liquid immiscibility.

The primary minerals of the gabbro layer are plagioclase, augite and magnetite. Secondary alteration has altered most of the augite to uralite. Plagioclase occurs as elongated laths, the only idiomorphic mineral present, with the allotriomorphic minerals of magnetite and augite occurring as grains between the plagioclase laths. Magnetite was the last mineral to crystallize and, because of the amount of vanadium incorporated in it, the magnetite gabbro layer has the potential to have economic value. The crystal form of the magnetite does not indicate the concentration of the magnetite by an accumulation of separate magnetite crystals; on the contrary, the textural features suggest the formation of a separate oxide liquid.

The enrichment of PGMs, in association with magnetite, has been described in other mafic ultramafic complexes. In association with the Main Magnetite Layer in the Upper zone of the Bushveld Complex, PGMs are concentrated in anorthosite just below the layer. However, the magnetite seams themselves contain very little PGMs.

In the Skaergaard intrusion in Greenland, palladium is concentrated with copper and gold in anorthositic layers associated with magnetite at the top of the middle zone, having values of up to 3 ppm Pd and 200 ppb Pt. In the Rincón del Tigre Complex in Bolivia, platinum and palladium are concentrated with copper at the base of the magnetite-bearing gabbro in the upper part of the intrusion with maximum precious metals concentrations of 1.8 ppm Pd and 0.68 ppm Pt in separate 1-m samples. In all of these intrusions, magnetite formed after extensive fractionation of the magma.

The sulphide content of the Rio Jacaré rocks is very low and the rocks are metamorphosed. Sulphides in the magnetite and magnetite bearing pyroxenite of the Lower zone show enrichment in platinum, palladium, rhodium, iridium, gold and nickel, but not in copper, compared to the Upper zone. Recalculated sulphide concentrations for samples from Campbell are similar to those of PGM-enriched sulphides from Birch Lake and Medvezhy Creek in the Norilsk Complex. In contrast, recalculated sulphide concentrations of the Gulçari B and Novo Amparo samples resemble the PGM-depleted Minnimax sulphides and Dunka Road sulphides of the Duluth Complex.

The vanadium at Maracás is associated with the titaniferous magnetite. Within the deposit, the titaniferous magnetite is the major oxide phase, followed by ilmenite. Magnetite occurs as primary grains that may be partly martitized. There is also fine-grained magnetite as inclusions in the silicate grains. This magnetite occurs as a secondary alteration after uralitization of pyroxene and serpentinization of olivine.

The magnetite normally occurs as anhedral grains, with grain sizes of between 0.3 and 2.0 mm, and forms a polygonal mosaic together with ilmenite. Ilmenite also occurs as inclusions in the magnetite, commonly displaying exsolution textures. Silicate phases associated with the magnetite include uralite, augite, plagioclase, hornblende, and rare grains of clinopyroxene, olivine and spinel. Magnetite from the magnetitite in the Lower zone (Campbell) has higher V2O5 concentrations (0.9% to 7.0%) than magnetite from the Upper zone (Gulçari B and Novo Amparo, 0.3% to 2.5% V2O5; Brito, 2000).

Rare olivine and pyroxene grains are observed within the magnetitite, but most are altered to serpentine or chlorite. The Rio Jacaré intrusion has been intensely metamorphosed, so the pyroxene compositions observed probably reflect metamorphic re-equilibration rather than original magmatic compositions. In addition, Brito (2000) also documented the presence of orthopyroxene. Garnet and biotite are present in the Gulçari B and Novo Amparo deposits.

The Maracás Vanadium Project is an open pit operation utilizing a contract mining fleet of hydraulic excavators, front-end loaders and 36 tonne haul trucks.

The disposal of waste rock, and low grade mineralized material will be executed on an area close to the pit. The site shall be adequately prepared to include drainage at its base and channels to direct the flow of water with the aim of aiding geotechnical stability and mitigating the erosion of the stockpiled material.

The operation of this phase, in accordance with the ascending method, shall begin during the construction of the heap at the base of this area. Waste rock will be disposed by truck, which will then be uniformly distributed and leveled by an operator using a tractor. The procedure is then repeated, stacking another bank above the original one, while maintaining a ramp for the trucks to be able to access the area.

The Maracás vanadium recovery plant was commissioned in 2015 and has been in startup mode for much of that time ramping up to near design capacity. At the time of writing this report, the plant produces up to 9,360 t of V2O5 equivalent per year with a trend approaching design capacity. Except for unanticipated downtime and subject to completion of the two expansions contemplated herein, production is expected to reach 13,200 t/a V2O5 in 2020.

The current process flow sheet comprises three stages of crushing, one stage of grinding, two stages of magnetic separation, magnetic concentrate roasting, vanadium leaching, ammonium meta-vanadate (AMV) precipitation, AMV filtration, AMV calcining, and fusing to V2O5 flake as final product.

Originally sized to process 960,000 tpy run of mine (ROM) the plant will be capable, after due modification, to process 1,900,000 tpy of feed ore with an average grade of 1.14% V2O5 and produce 9,600 t/y V2O5.in 2017. In 2020 after completion of two expansions it is expected that the Project will produce 13,200 t/y V2O5 the plant is designed to operate 365 days per year, 7 days/week, and 24 hours/day with an on stream factor of 85%.

Overall recovery from ore for V2O5 has reached 76.5% during Q3 2017, and is expected to reach 76% over the life of mine.

The ore is crushed via a three-stage crushing circuit comprising a primary jaw crusher, a secondary cone crusher and a vibrating sizing screen. The fine crushed product is fed to a 4,200- m³-capacity stockpile from which it is withdrawn at a controlled rate to feed the grinding circuit. The grinding mill grinds to a product size of minus 150 microns.

The vanadium is contained within the magnetite fraction of the resource. Magnetite is recovered by using low intensity magnetic separator (LIMS) of 1,500 Gauss. There are 4 (four) roll magnetic separator Imbras of 36”x120” with 150t/h of capacity. The separation is done in the unique step where the pre magnetic concentrate is blended with the massive material and sent to the milling circuit.

The magnetic separation product is sent to the stock pile to feed the milling circuit. The objective is to feed the mill with a magnetic grade of +45%.

This step of processing uses a ball mill in a closed circuit with hydrocyclones. The mill dimensions are 13x26’, with 2.275 KWh (3.000 HP). The hydrocyclnes are comprised of 4 (four) Cavex 500 with 2 (two) operating and 2(two) in standby.

The mill works with maximum ball size of 90mm (Magoteaux), with a consumption of 250 g/t.

The product of this process is a P80 with 86 microns with variation of 43%.

This milled material is processed in the low field magnetic separation (LIMS) of 1,500 Gauss, in the circuit with 1 (one) stage rougher and 2 (two) cleaner. There are 4 (four) magnetic separator Imbras, WD 48x125” with capacity of 60 t/h. The mill feed is 2.270t/day or 128t/h with efficience of 74,1% .

The final magnetic concentrate will be thickened and filtered. The filter mat (Westech) of 20m2 with capacity of 53,2 t/h cake will be fed to the roasting section of the plant. The nonmagnetic tailings fraction from the beneficiation plant are thickened, filtered and conveyed to the tailings pond.

The wet magnetic concentrate filter cake, containing approximately 3.21% V2O5, is roasted at high temperature (+1,100 °C) in a rotary kiln (FLSmidth) with diameter of 4,2m and length of 90m with spin of 1 rpm. The kiln capacity is of 88 t/h. At the kiln feed is add at the mold 51 kg/t of sodium carbonate (Na2CO3) and 12 kg/t of sodium sulfate (Na2SO4). This material is roasted until the temperature metioned before (1.100 ºC) where magnetite Fe3O4 is oxided to hematite Fe2O3, losing the magnetic caracteristc after 3 hours of roasting. The vanadium the extract from magnetite structure in the Salt Vanadium. The consumption of HFO+Diesel at kiln is 34 kg/t.

The oxided material its cooling in the rotary cooler (FLSmidth) with diameter of 4m and length of 34 m with spin of 2 rpm. The fully rotary cooler is of 56t/h.

After reducing the size, this product roasting and cooling is fed to the leaching process.

The Vanadium salt contained in the roasted calcine is then leached for one hour and twenty minutes in each of the two agitated tanks installed in series of 120m3 of capacity.

The feed rate between august/2016 to may/2017 was of 1.115t/dia and the efficiency of 79,8%. Similar operation has efficiency of 85%.

The leach discharge is send to thickner (Westech) with 14m of diameter and then filtered and washed using a vacuum belt filter. The solution containing approximately 110 g/L V2O5 is pumped to chemical plant for de silication stage.

The cake has 10% of moisture and this product have a concentration of 60% Fe, 2,9% SiO2 and 6,8TiO2.

Largo hopes ot be able to sell this “cake” from leach stage at some point in the future, notwithstabnding that product has a high TiO2 grade and a low Fe grade. It may be possible to blend it with richer magnetite concentrate, which can be found in the region, to create a saleable product.

After desilication, the solution is pumped to a filter (Andritz, 1200 x 200) with 72 plaques with 16,7 m3 /h where the solids are removed and sent to disposal along with the effluent tailings from the evaporator/precipitation. The filtrate, pregnant leach solution (PLS), is pumped to the precipitation stage.

The precipitate is filtered, washed, and fed to a dryer prior to being calcined to produce V2O5 powder. The barren solution, which contains sodium and ammonium sulphate salts, is treated to recover ammonium sulphate, which is recycled to precipitation, and sodium sulphate part of which is recycled to the roasting stage.

A crystallization circuit has been designed to recover sodium sulphate salt, and ammonium sulphate solution from the barren leach liquor.

The barren liquor, which contains ammonium sulphate, sodium sulphate plus small amounts of dissolved AMV and impurities, is first concentrated by evaporation to a predetermined ammonium sulphate concentration.

As they this barren have the concetration of 250g/l of Na2SO4, the salt start to precipitate. The pulp with 20% of solid, it is pump to cyclone where the underflow feed a centrifuged. This centrifugal produce salt sulfate solid with 5% of moisture. The overflow material (ammonium sulphate) is sent back to precipitation stage and a portion of this slurry is purged to a sealed purged dam as a mean of controlling chlorides build up in the circuit.

Wet AMV (15%) solids are dried in a flash dryer (Drytech) with capacity of 6t/h of air. The dried AMV is calcined under oxidizing conditions to produce V2O5 and then melted and cast into flakes for sale.