In the Aley deposit, niobium occurs in pyrochlore that formed as early-stage mineral precipitates in primary magma. Alteration of the dolomite carbonatite by unknown factors created the Nb bearing alteration minerals fersmite and columbite. The changes are believed to have occurred largely in situ, and as such there has been less scope for transport or concentration of Nb by secondary processes. The type of deposit is considered to be that of magmatic segregation.

The Aley Carbonatite complex intrudes Cambrian to Ordovician sedimentary rocks of the Kechika (limestone), Skoki (dolomite to volcaniclastics) and Road River Group formations (clastic sedimentary rocks). The intrusion is ovoid in plan view with a diameter of approximately 2 km and surrounded by a fenite aureole up to 500 m thick that has previously been mapped as “amphibolite” (Pride, Cominco Ltd., 1987) and “syenite” (Mäder, 1986). The intrusive contacts are parallel to bedding and lie at a uniform stratigraphic level near the base of the Kechika Formation. Three principal units within the carbonatite have been identified:

1) a volumetrically dominant fersmite- and pyrite-bearing dolomite-apatite carbonatite unit that forms the core of the sill;
2) a magnetite, pyrochlore, phlogopitebearing calcite-apatite carbonatite unit that forms the margins of the sill where it is in contact with the Kechika Formation; and
3) a banded magnetite-apatite unit in the dolomite core.

The niobium (Nb) minerals at Aley consist of pyrochlore, fersmite, and columbite. The alteration follows a general sequence whereby pyrochlore, and to a lesser degree, columbite, alter to fersmite. The chemistry of the alteration minerals appears to be inherited from the parent mineral. At Aley, no significant amount of tantalum (Ta) has been noted in the pyrochlore and the alteration minerals also do not contain it. Likewise, the reduction of solid solution capacity in the minerals reduces in the alteration sequence. The iron (Fe) content appears to increase in atomic proportion towards columbite.

The two largest exploration targets are the Central and Saddle zones. The Central Zone occupies the core of the carbonatite complex and has a strike varying from 070° to 120° (predominantly 120) and dips 60° to 70° to the south. It is roughly ovoid in shape and extends some 1400 m E-W, up to 725 m N-S, and over a vertical range of 650 m. Mineralization is associated with bands and swirls of magnetite. The Saddle zone occupies the northern part of the carbonatite complex in proximity to the contact with the amhibolite annulus and has a strike of 070° to 090° dipping at 60° to 70° to the north. Mineralization is associated with alternating bands of pyritic calcite (varying in width from 5cm to 5m) with dolomitic or calcitic carbonatite.

The Aley open pit will be mined by a conventional truck and shovel operation. Due to the production rate, location of the deposit and the width of the mining cuts, the equipment utilized in this operation will be approximately one third of the size of typical equipment found in today’s large open pit operations.

The production rate of 10,000 tpd ore was selected as a base case for project design and costing on the basis of balancing economies of scale and niobium market conditions.

Designs for the Aley pit phases use a fixed face slope angle of 65 degrees and safety berm widths of 10m for every two vertical 10m benches, for a standard inter-ramp slope angle of 46 degrees. Knight Piesold’s recommended inter-ramp pit slopes for different sectors of the pit are:
- 10m vertical benches, double benching configuration (safety berm every 20m);
- North Sector: 70 degree face angle, 50 degree inter-ramp angle, berm width of 9.5m;
- North-East Sector: 65 degree face angle, 48 degree inter-ramp angle, berm width of 9m;
- South-East Sector: 70 degree face angle, 50 degree inter-ramp angle, berm width of 9.5m;
- West Sector: 65 degree face angle, 45 degree inter-ramp angle, berm width of 11m.

The following parameters were used to drive the production schedule and equipment requirements:
- Annual mill feed of 3,650 ktpa is targeted based on 10,000 tonnes/day ore milling;
- Year 1 milling target of 7,500 tonnes/day;
- Year 2 milling target of 9,675 tonnes/day;
- Year 3 onwards milling target of 10,000 tonnes/day;
- Cut off grade of 0.3% Nb2O5;
- The annual periods for mining are 360 operating days assuming 5 days down due to weather.

The mining operations will be typical of similar open pit operations in mountainous terrain. Direct Mining includes, drilling, blasting, loading, hauling, pit support, ground support and unallocated labour activities in the mine.

Run-of-mine (ROM) ore from the open pit mining operation is trucked to the 350HP primary jaw crusher and dumped onto a vibrating grizzly screen. Screen undersize material is passed to a conveyor and transported to a coarse ore stockpile. Oversize material reports back to the jaw crusher. The jaw crusher crushes the ore to a product size of 80% passing 150 mm. A belt conveyor transports the crushed ore to a coarse ore stockpile with a live capacity of 15,000t, located adjacent to the concentrator building.

Crushed ore from the stockpile is reclaimed by a set of three 25HP apron feeders, feeding the mill at 10,000 tpd. The coarse ore is fed to 24’ diameter SAG mill with a 5361HP drive motor. The product is discharged onto a 2.4m x 6.1m screen where the oversize product is recycled back to the feed of the SAG mill. Screen undersize slurry product is pumped to a primary cyclone cluster. The cyclone underflow feeds the 18’ x 27’ ball mill, which is sized with an identical motor to the SAG mill. Ball mill discharge reports to the same cyclone feed pump box as the SAG mill discharge screen underflow.

Primary cyclone overflow, at a size of 140um, is collected in a pump box and pumped to a secondary cyclone cluster. The cyclone underflow feeds a 4500HP tower mill. The tower mill discharges back to the primary cyclone overflow pump box. This tertiary stage of grinding is designed to produce a product size of 80% passing 50 µm.

An equipment list has been developed for the crushing and comminution sections of the process facilities. This portion of the equipment list details the characteristics and specifications for over 250 separate pieces of equipment. Total peak power in crushing and comminution is 12,500 kW. Major equipment connected power in crushing includes one 20 kW scalping grizzly screen, one 260 kW jaw crusher, and two coarse ore feed conveyors totalling 395 kW. The balance of the crushing connected power is distributed among support and ancillary area equipment such as heaters, lube skids, and air supply. Major equipment connected power in the comminution section includes three 75 kW apron feeders, one 4000 kW SAG mill, one 4000 kW ball mill, one 3400 kW vertical grinding mill, and 2400 kW in major pumping stages. The balance of the comminution connected power is distributed among support and ancillary area equipment such as slurry pumps, heaters, lube skids, and air supply.

The proposed processing facilities for the Aley project are all sized for a minimum 10,000 tpd throughput with an overall processing plant availability of 92 %. Run of mine ore is to be delivered to a single stage crushing facility. Crushed product is then transferred via conveyor to a single coarse ore stockpile. This stockpile is used to feed a three stage comminution circuit that consists of a semi autogenous grinding (SAG) mill, a ball mill, and a fine grinding mill with the appropriate size classification circuits. Final comminution product is fed to the concentration plant, details of which are proprietary and confidential. An upgraded concentrate from the concentrator is fed to a leach facility for further processing, while waste streams produced in the concentrator are recombined and pumped to a sand storage management facility (SSMF).

Leached concentrate residue is then processed through a calciner and proceeds to ferro-niobium conversion. Converter waste is stored ........