At Holt-Holloway, the gold mineralization is quite unlike the classical Superior province auriferous quartz vein systems resulting from deformed, extensional fracture arrays. Rather, it is associated with disseminated sulphides in altered rock, sometimes described as replacement mineralization. Mineralization typically consists of moderately to steeply dipping tabular zones of disseminated pyrite (generally less than 5 per cent per volume) and gold in intensely altered tholeiitic basalt, with variably developed microveinlet stockworks. The ore is gold rich (Au:Ag is greater than 5) and contains concentrations of arsenic. The mineralized zones occur in a variety of geological settings reflecting a variety of controls on the localization of the mineralization: along low-strain lithological contacts (Lightning, Blacktop and Smoke Deep zones at Holloway), along brittle and/or ductile faults (McDermott, Worvest and Mattawasaga zones), and as shallowly dipping discordant zones (Tousignant, South Zone and Zone 4) of which the South Zone (Holt) is spatially coincident with an array of shallowly dipping syenitic dykes. Mineralized zones are coincident with zones of intense albite ankerite alteration of the host basalt, which, in turn, are partly fringed by sericite alteration haloes at Holloway and fringed by broader zones of calcite alteration. Disseminated specular hematite can be present within or outboard of mineralized zones.

Gold mineralization at the Holt and Holloway Mines is associated with replacement carbonate pyrite-albite-quartz alteration that overprints mafic volcanic rocks in, and adjacent to, D3-D4 high strain zones. The overprinting of multiple mineralization phases in the same area suggests that mineralization was long lived and spanned syntectonic deformation during exploitation of the same fluid channel ways.

The deposit types vary within the Taylor Mine Complex. The Shaft Deposit furthest east is identified as a Felsic intrusive related model, with a contemporaneous green carbonate association. Feldspar porphyritic intrusions are the host to high grade gold veins and high concentrations of disseminated sulphides (generally pyrite).

Within the West Porphyry Deposit, free gold is found within quartz dominant extension veins and veinlets, cross-cutting the foliation present within the chrome-mica and chloritic altered ultramafic rock. This unit can be up to 20 m thick as the true extent of the veins are not fully understood. Additionally, the main shear (interpreted to be the contact of the PDF between the mafic and sediment contact, is host to a quartz brecciated shear vein, which can be up to 2m thick. Altered mafic units consisting of high concentrations of disseminated sulphides are also host to gold mineralization.

The Taylor Mineralization is in close proximity, within the hanging wall, to the PDF. Over a strike length of 2.3 kilometres there are three mineralization zones that have been identified. From east to west these are:

- The Shaft Deposit, with gold mineralization associated with felsic intrusive rocks.

- The West Porphyry Deposit (WPZ), a system of stacked lenses, with the gold mineralization associated with felsic intrusive and altered mafic-ultramafic rocks (Green Quartz Carbonate).

- The Shoot Deposit, with gold mineralization hosted by argillaceous metasedimentary rocks within a package of green quartz carbonate. Gold commonly occurs as relatively coarse-sized free gold in quartz, but also occurs as fine particles, which may be intimately associated with sulphides (particularly pyrite and locally, arsenopyrite) both in quartz-carbonate veins or in surrounding altered host rocks.

The primary stoping method at the Holt Mine is mechanised long hole drilling and blasting within the mining blocks with rail transport to the shaft ore passes. The spacing between sublevels for long hole stoping varies between 20 m and 17 m, depending on the dip of the ore. Mechanized long hole stoping is planned to be used in all zones at the Holt mine. “Drift and pillar” stoping may be needed in some areas where the ore is too shallow and not amenable to long hole methods. Drilling is performed with tophammer drills, with hole sizes ranging from 64 mm to 76 mm in diameter.

The Tousignant Zone is planned to be mined with modified room and pillar.

Zone 4 is accessed by mechanised equipment via ramps and sublevels connected to two main rail haulage levels 925 and 1075. Zone 4 is divided into two mining blocks: the upper mining block represents the stopes reporting to the 925 haulage level and the lower mining block represents the stopes reporting to the 1075 haulage level. The use of both haulage levels provides increased flexibility to the overall Holt mine plan.

The mine extraction sequence for Zone 4 is using a primary-secondary stoping arrangement with cemented rock fill being used in the primary stopes. Strike length is set at 15 m for the primary stopes and 20 m for the secondary stopes. Sublevels in Zone 4 are spaced 17 m apart due to the shallow dipping nature of the ore within the zone. The current mine plan includes stopes being mined using up holes, with the remainder of the stopes being mined using down holes. This method of combining up and down hole configurations helps minimize hole length and increases accuracy of hole drilling.

Zone 6 is planned to be accessed via a ramp system and sublevels spaced at 20 m intervals for “conventional long hole” stoping. Accesses will be connected to haulage levels on 925, 775 and 1075 via drifts and ore passes.

The mine extraction sequence for Zone 6 is using a primary-secondary stoping arrangement with cemented rock fill being used in the primary stopes. The strike length is set at 20 m for all stopes (primary and secondary). The delivery of cemented rock fill to the upper portion of the zone will be initiated from the 435 level cement plant. From here a slurry hole has been drilled down to 775 level backfill system, which will deliver cement to the lower portion of the zone. Secondary stopes are planned to be filled with rock fill produced during development of the ramp and footwall drifts.

Upper Zone 6 is currently transitioning to the Avoca mining method for the extraction of its reserves. If proven to be viable, it is expected that this mining method will be incorporated into the lower portions of the zone.

Ore will report to one of three rail haulage levels (775, 925, or 1075 level, depending on the stopes elevation) via an internal ore pass system. Ore will then be trammed on rail to the shaft ore pass system.

Zone 7 is planned to be accessed via a ramp system and sublevels spaced at 20 m intervals for open stoping. Accesses will be connected to the 435 haulage level via drifts and ore passes.

The mine extraction sequence for Zone 7 is using a primary-secondary stoping arrangement similarly to Zone 6. Cemented rock fill being will be used in the primary stopes and secondary stopes will be filled with rock fill produced during development of the ramp and footwall drifts. The strike length is set at 20 m for all stopes (primary and secondary). The delivery of cemented rock fill to the upper portion of the zone will be initiated from the 435 level cement plant.

V-93 is a steeply dipping ore body located to the south of Zone 4 and above 775 level on the west end of the mine. The mineral reserves for V-93 are estimated at 100,184 tonnes grading at 4.59 g/t.

V-93 Zone is planned to be accessed from a ramp system connected to the 775 level with sublevels spaced at 20 m intervals. The zone is planned to be mined using longitudinal long hole retreat method. The stopes will be backfilled using cemented rock fill from the planned 775 level backfill system. Rock fill will be provided from development headings or could be trammed from Zone 6 development when available.

Taylor Property.
Overhand Cut and Fill (OC&F) and Drift and Fill (D&F) were selected as the most suitable mining methods:
- Where the ore is dipping at less than 45° and the ore horizontal width is narrower than 10 m, OC&F is the method of choice;
- Where the ore is dipping at less than 45° and the ore horizontal width exceeds 10 m, D&F will be the method of choice.

The Holt Mill was constructed in 1988 and was originally designed for a throughput of 1,360 tpd. Expansions in 1988 and 2001 increased the throughput to 2,500 tpd and 3,000 tpd, respectively.

Surface ore storage is a total of 4,900 t in three silos, the Holt headframe bin (900 t) and two other separate storage bins (1,000 t and 3,000 t). Ore can be delivered to the mill from the Holt Mine by conveyor or from a separate surface dump that enters a 100 tonne hopper, and then can be fed to either of the two storage bins.

The grinding circuit consists of a 5 m diameter by 6.1 m long Allis Chalmers ball mill, converted to a SAG mill, a 4 m diameter by 5.5 m long Allis Chalmers ball mill and a 3.6 m diameter by 4.9 m long tertiary ball mill, all operating in series and in closed circuit. The details of the grinding circuit are shown below in Table 16-1. The grinding circuit is controlled by a Wonderware system and Modicom programmable logic.

The primary cyclone cluster consists of six 381 mm (15”) Krebs D15B cyclones. A secondary cyclone cluster consists of twelve 254 mm (10”) Krebs gMAX cyclones with an Outokumpu PSI-200 online analyzer. The secondary cyclone cluster feeds a 27 m (90 ft) Eimco thickener. The thickener underflow feeds a pre-aeration tank, which gravity feeds five carbon-in-leach (CIL) tanks in series. The tank system is conventional gravity flow for slurry with counter-current carbon advancement

Precious metal stripping is performed in batch operations, advancing 2.7 t of loaded carbon through a 1.2 m by 2.4 m (4 ft x 8ft) Simplicity screen. Carbon is transferred to an adsorption column where a Zadra process is utilized as the gold elution method. Barren solution is circulated through two shell and tube heat exchangers and a 360 kW electric inline heater.

The resulting pregnant solution is pumped from the solution tank to an electro-winning cell. The gold precipitate is further refined using a 125 kW Inductotherm furnace and the doré bars are poured in a seven mould cascade arrangement. After stripping, the carbon is regenerated in a rotary kiln, quenched, screened and returned to the process. Carbon fines are collected in a tank, filtered in a Perrin press, and packaged for sale.

Reagents and operating supplies for the mill, such as process chemicals and grinding steel, are stored in the reagent storage building attached to the concentrator at the south end of the building.