The Hemlo gold deposit has been interpreted as a porphyry-style deposit genetically linked to the Moose Lake porphyry complex (Kuhns, 1988; Kuhns et al., 1994; Johnston, 1996).

The Hemlo Mines Operation consists of David Bell, an underground mine, and Williams, an underground and open pit mine.

The Alimak mining method was introduced at the David Bell Mine in 1998 to extract an otherwise uneconomic and inaccessible reserve. The success associated with the extraction of these reserves lead to an expansion of the method to include a reserve of almost 200,000 tonnes. To date results have been extremely positive in terms of grade control, reduced dilution, stope recoveries, productivities and mining costs. As a direct result Alimak mining is now an integral part of the current mining plan for present and future reserves. It is hoped that through further development of the method at David Bell Mine we will continue to see positive results in these areas and be able to increase mineable reserves to include proven resources that do not currently meet the criteria of our current stoping plan.

Barrick Hemlo is a combination of two mine properties (David Bell Mine and Williams Mine). All of the major cyanide facilities are associated with the Williams Mine. The David Bell Mine has a paste plant, thickener and associated pipeline system. The operations of the David Bell Mine and Williams Mines are managed as a single operation. The operation refers to itself as Barrick Hemlo (Hemlo).

The active cyanide facilities at the Hemlo operation include:
- Grinding Circuit
- Gravity Concentration Circuit
- Pre-Leach Thickener
- Cyanide Storage Tank and Offload Facility
- Cyanide Leach Circuit
- Carbon-In-Pulp (CIP) Circuit
Carbon Strip Circuit
- Barren Solution Tank
- Loaded Solution Tank
- Tailings Pump Box
- Tailing Management System (TMS – includes tailings pond and polishing pond)
- TMS pipeline systems
- Williams Paste Plant
- David Bell Paste Plant

All milling is performed at the Williams Mill. The grinding circuit includes two parallel trains, each comprised of a semi-autogenous grinding (SAG) mill, a ball mill, and primary and secondary cyclones.

The gravity concentration circuit in each grinding train employs a Knelson concentrator for gravity gold recovery. The grind slurry enters a large pre-leach thickener at approximately 25 percent solids, and the resulting thickener underflow is transferred to the cyanide leach circuit at approximately 50 percent solids.

The cyanide leach circuit consists of nine leach tanks; however, the operation varies the number used from seven to nine depending on operational needs. Gold is extracted from solution in the CIP circuit, which consists of six tanks. Loaded carbon is stored in two storage vessels. Acid and caustic are used in the carbon strip circuit and the loaded strip solution is pumped to a surge tank prior to entering the electrowinning circuit located within the refinery. Barren strip solution is stored in a surge tank adjacent to the loaded strip solution surge tank. The stripped carbon is reactivated via acid washing and a regeneration kiln.