The Hallmac mine is situated at 1677 metres elevation above sea level, on the southeast side of Mount Payne in the Slocan Mining Division. The property includes the Altoona, Bowknot and Tawanda claims (Lots 1918, 1919 and 1920, respectively).

Sandon Mining & Milling Company, Limited Liability held the property from about 1898. Underground work in 4 adits totalled about 460 metres. The company charter was surrendered in 1912 and the claims eventually reverted to the Crown for taxes.

The Altoona claim was re-Crown-granted to A.J. Murphy, of Sandon, in 1926. Altoona Mines, Limited was incorporated in August 1929 to acquire the Altoona and Bowknot Crown-grants and the Commander located claim. Work during 1930 included trenching and a short crosscut driven from No. 1 adit; the claims were subsequently abandoned.

The claims were acquired by E. Doney in 1949 and optioned the following year to Kootenay Belle Gold Mines, Limited, operator of several properties in the Sandon area. Ore from stopes in No. 1 and 2 adits was shipped to the Whitewater mill during 1950-51.

During 1965-66 Sven Hallgren and associates carried out mining in No. 1 adit under the name Hallmac Mining Syndicate. The Altoona and Bowknot claims were optioned from E. Doney by A. Hewitson in November 1968 and assigned to Hallmac Mines Limited in January 1969. In addition the company acquired the Tawanada Crown-grant, the Hall 1-3 located claims, and the adjoining Majestic property (082FNW017). Intermittent work to 1980 included geological mapping, crosscutting on No. 2 level, diamond drilling, and a geochemical soil survey. In 1981-83 development and mining operations were carried out in two adits vertically apart on a new showing discovered in 1980. A third adit was begun in 1983 on a newly discovered adjacent structure. Operations were suspended in 1984 due to the low silver price. The company name (Hallmac) was changed in February 1986 to Royal Oak Resources Ltd. The mineral inventory at closure in 1984, including stockpiled high-grade and mill feed and ore in place is estimated to contain 7,651,500 grams of silver, 726 tonnes of lead and 193 tonnes of zinc (Royal Oak Resources Ltd. June 30, 1986 Annual Report).

Regionally, the area lies on the western margin of the Kootenay Arc, in allochthonous rocks of the Quesnel Terrane. In the vicinity of the occurrence, the Quesnel Terrane is dominated by the Upper Triassic Slocan Group, a thick sequence of deformed and metamorphosed shale, argillite, siltstone, quartzite and minor limestone. Rocks of the Slocan Group are tightly and disharmonically folded. Early minor folds are tight to isoclinal with moderate east plunging, southeast inclined axial planes and younger folds are open, southwest plunging with subhorizontal axial planes. The sedimentary sequence has been regionally metamorphosed to lower greenschist facies.

South of the occurrence, the Slocan Group has been intruded by the Middle Jurassic Nelson intrusions which comprise at least six texturally and compositionally distinct phases ranging from diorite to lamprophyre. The most dominant phase is a medium to coarse grained potassium feldspar porphyritic granite. Several feldspar porphyritic granodiorite dikes, apparently related to the Nelson intrusions, also cut the sedimentary sequence near the occurrence (Paper 1989-5).

The Hallmac mine area is underlain by a sequence of siltstone, argillite, carbonaceous graphitic and pyritic slate, phyllite and quartzite of the Slocan Group. The sedimentary rocks have been intruded by porphyritic and aplitic dikes and sills apparently related to the emplacement of the Nelson intrusions.

The sedimentary rocks strike 310 to 320 degrees and dip steeply east and west. Within individual beds, crenulations related to soft sediment deformation are evident. A penetrative axial plane cleavage occurs subparallel to the bedding. This is best developed in the more phyllitic units. A more pronounced fracture cleavage, generally normal to bedding, is characteristic of the slates.

Sedimentary rocks and dikes are cut by fractures, joints and faults along several diverse directions. Two fault orientations, one striking 070 degrees and dipping 58 degrees southeast, and the second striking 068 degrees and dipping 39 degrees southeast, appear to be favourable for economic mineralization.

Very low rank regional metamorphism has converted former shales and mudstones to slates and phyllites. Minor biotite occurs along narrow (25 millimetre) "bake" zones adjacent to intrusive contacts.

Argentiferous galena with variable amounts of sphalerite and minor tetrahedrite and arsenopyrite occurs in a siderite-quartz- calcite gangue in brecciated vein structures crosscutting argillite-slate-quartzite host strata. The silver-bearing galena varies from coarse, massive aggregates to fine, foliated or lineated "steel" galena. Similarly, sphalerite in the zinc-rich veins varies from clusters of coarse subhedral brown crystals to very fine, dark brown to nearly black (iron-rich) massive aggregates.

The brecciated fault controlled vein structures strike in a general 070 to 085 degree direction and dip from 50 to 65 degrees southeast. Pinching and swelling is common and vein structures can vary in width from 0.25 to over 2 metres. Average mining width is about 1 metre. Galena can occur in aggregates, pods, lenses and sinuous bands along the footwall, hangingwall and within the fissure structures. This, together with the friable nature of the oxidized breccia host, has made control difficult. Extensive timbering and rock-bolting was required for ground stabilization in stoping areas (Assessment Report 18551).

Work done to date suggests there is a vertical transition from galena to sphalerite between the 1735 and 1690 levels. Silver grades appear to decrease somewhat in the high zinc zone.

Extensive surface oxidation has penetrated the vein structure and oxide contamination is prevalent throughout the galena-bearing lodes. However, mineralization intersected in the 1988 underground program comprises clean, unoxidized sulphides indicating the limit of surface oxide contamination has been passed in this area of the mine.

Just above the 1735-metre elevation west of section 83740E (mine grid), the main Hallmac zone bifurcates downward into two separate vein lodes termed the Footwall (FW) and Hangingwall (HW) zones, respectively. Exploration to date suggests that the HW zone pinches out at about the 1725-metre elevation east of 83740E; this is conjectural, however, due to lack of drilling data. Though apparently locally offset by sinistral north-northeast striking faults, the main FW zone of the Hallmac system is more or less continuous on strike for at least 250 metres (Assessment Report 18551).

In late 1984, a 1-metre wide section of zinc-silver mineralization was exposed in a crosscut which crossed the FW zone at the east end of the 1690 level. This discovery suggested that the limits of the effects of surface oxidation had been reached (on the 1690 level at least) and that uncontaminated commercial ore might be intersected east to the crosscut exposure (Assessment Report 18551).

Based on a diamond drilling and underground exploration program in 1988, the mineral inventory (indicated/probable/possible reserves) of the Hallmac mine was 11,398 tonnes of ore grading 778.1 grams per tonne silver, 7.75 per cent lead and 2.84 per cent zinc (Assessment Report 18551).

Past production from the Hallmac between 1951 and 1990 yielded about 7754 kilograms of silver, 874,298 kilograms of lead, 172,704 kilograms of zinc, 382 kilograms of cadmium and 703 grams of gold from a minimum of 8041 tonnes mined.