The Mountain Boy past producer is located about 1 kilometre west of American Creek, approximately 5 kilometres north of the confluence of American Creek with the Bear River, 24 kilometres north of Stewart.
The area is underlain by north trending, west dipping rocks of the Lower Jurassic Unuk River Formation (Hazelton Group). These lie on the west limb of the north-northwest trending American Creek anticline. Red to green porphyritic andesites and tuffs are intruded by numerous dikes of feldspar porphyry, augite porphyry and lamprophyre. Near the mineralization there are several zones of intense shearing and numerous faults and fractures.
Mineralization on the property consists of at least seven main (Mann, High Grade, No. 3, DeMann, Franmar, Four Bees and South Mann) and four minor (North, WoMann, Waterfall and Fault Breccia) replacement zones tested with trenches, previous open cuts and/or adits (Figure 5, Assessment Report 36417).
Mineralization occurs along wide bodies consisting of mainly barite, quartz, jasper, carbonates (calcite, siderite, rhodochrosite and possibly smithsonite and witherite) and sulfides (sphalerite, galena and minor chalcopyrite, bornite, tetrahedrite, jamesonite, covellite, acanthite, stromeyerite and greenockite) as well as inclusions of altered country rock. Native silver occurs along a zone traced for at least 20 metres of strike length on the High Grade vein. Secondary weathering minerals namely malachite, azurite and hydrozincite are common particularly in underground workings and along surface fractures.
The sulfides occur in the replacement bodies as coarse grains, wispy stringers and semi-massive veinlets associated with discrete lenses and stringers of quartz rich material bound by low sulfide bearing barite and calcite. High sulfide content appears to be directly dependent on quartz or silica content. Sphalerite is by far the most dominant sulfide and comprises over 70 per cent of the sulfide content. Highest sulfide values do not necessarily yield the highest silver values.
The Mann (No. 1) vein is about 150 metres east of, and 150 metres below, the High Grade (No. 2) vein. A third vein (No. 3) outcrops about 100 metres west of the High Grade vein.
The Mann vein, outcropping on the Mountain Boy and Hard Money claims, trends north to northeast and dips 45 to 65 degrees southwest. It can be traced for about 200 metres to the south, where the South Mann tunnel (on the Hard Money claim) exposes the vein (or a branch thereof). In the main Mann tunnel, the vein is 10.7 metres wide and comprises mainly quartz with lesser barite and calcite. Galena and sphalerite form semi massive ribbons in the vein and stibnite, chalcocite and argentite have also been reported. The best mineralization occurs on the footwall of the vein. Chip samples from the Mann tunnel assayed up to nil gold, 1848 grams per tonne silver, 1.83 per cent zinc, 0.58 per cent lead and 0.20 per cent copper across 2.1 metres (Property File - Mathews, 1942).
The High Grade vein, outcropping on the Mountain Boy and Hard Money claims, strikes north at its northern end but curves to the southeast at its southern end. It dips 20 to 25 degrees west and can be traced for about 365 metres along strike. The vein is cut off at the south end by a fault. Nearby, east-trending faults exhibit dextral lateral displacement of the vein. The vein, up to 5 metres wide, comprises sparsely mineralized quartz, jasper and barite. The highest grade mineralization occurs across a 0.2 to 0.5 metre width along the footwall where pods and veinlets of sphalerite, galena, chalcopyrite, chalcocite, argentite, native silver, stromeyerite and pyrargyrite occur. Silver values are reported to average 7217 grams per tonne across 4.1 metres from the discovery outcrop (Property File - Mathews, 1942, page 6). Chip samples from the surface, immediately north of the Daly tunnel, assayed up to 0.51 gram per tonne gold, 17,493 grams per tonne silver, 4.2 per cent zinc, 1.7 per cent copper and nil lead across 0.61 metre (Property File - Mathews, 1942).
The No. 3 vein, outcropping on the Mountain Boy claim, strikes north to north-northwest and dips 30 degrees west. The vein, lying about 100 metres west of the High Grade vein, can be traced for about 500 metres. Details of the vein are not known. Vertical chip samples across the apparent width assayed up to trace gold and 13,694 grams per tonne silver across 0.9 metre (Property File - Sketch Map, 1936).
The DeMann zone has been the least tested of the zones due to the steep nature of the area in which it occurs. It outcrops along the south bank of Big Rock Gulch and appears to strike approximately 260 degrees azimuth and dip to the southeast. It has been traced over a length of 120 metres with the width of the zone varying from 2 up to 13 metres but generally averaging 8 metres. It is speculated that the DeMann vein is the location of the reported “Jewelry Shop” in a 1998 report by McIntyre. Apparently, the Cameron Tunnel was driven in order to intersect the “Jewelry Shop” at depth. Based on field observations, the DeMann vein consists of barite-jasper-quartz-calcite with local concentrations of sphalerite, galena, chalcopyrite and tetrahedrite.
The Frammar showing consists of a jasper-barite-quartz-calcite stockwork in red to maroon volcanic breccia approximately 160 metres southeast and 70 metres lower in elevation from the Mann adit. The zone strikes 320 degrees azimuth and dip 45 degrees to the west. It is exposed over a strike length of only 30 metres with both the north and south sides obscured by overburden. The zone, up to 7 metres wide, contains generally sparsely mineralized quartz stringers cutting silicified volcanics mineralized with sphalerite, galena and chalcopyrite as well as minor barite and tetrahedrite. The quartz veinlets contain sparse blebs of tetrahedrite and bornite. Strong hydrozincite and minor malachite were noted along fractures.
The Four-Bees zone is a wide northeast trending zone approximately 160 metres south of the Mann zone and 40 metres west of the Franmar zone. It consists of a mineralized zone up to 26 metres wide exposed over a length of 40 metres on a narrow ridge along the lower slopes of the property. It consists of 16.5 metres of a sparsely mineralized baritequartz-calcite-jasper vein with 9.9 metres of fractured and mineralized wall rock along its west side. The barite-quartz-calcite-jasper vein contains sparse sphalerite, galena and chalcopyrite as well as minor bornite and local tetrahedrite. Sulfides are generally less than 5 per cent of the zone. The wall zone contains semi-massive veinlets of sphalerite and galena as well as coarse blebs of chalcopyrite in quartz veinlets. Overall sulfides content of the wall zone is less than 3 per cent over the 9.9 metres.
The South Mann zone strikes approximately east west and dips to the south at about 35 degrees. It varies from 4 up to 6 metres in width and has been traced over a strike length of 200 metres (from the Cameron adit area to the South Mann adit). The South Mann adit was located just below the most southeast exposure of the vein. The back to the adit has broken through to surface along a diabase dike. The vein is predominantly barite-quartz-calcite-jasper with generally sparse sphalerite, galena and chalcopyrite. Sulfides are generally less than 5 per cent of the rock. However, in Trench 16, coarse-grained galena and sphalerite formed up to 20 per cent of the rock over widths up to 1 metre.
The North zone is an east-west trending vein that is up to 4 metres wide exposed along a strike length of 50 metres. It is obscured by overburden to the east and it splits into a series of mineralized stringers to the west. It consists of a barite-quartz-calcite-siderite-jasper zone with stringers of massive galena stringers up to 0.15 metre in width. Minor sphalerite and chalcopyrite are also present within the zone. Immediately above the North adit, abundant rhodochrosite associated with green sphalerite was noted in Trench 3. Overall sulfide content of the North zone is approximately 5 per cent.
The WoMann vein is just above the Mann adit and consists of several narrow 1-metre veins striking approximately east west and dipping 45 to 50 degrees to the south. Overall width of the zone is approximately 4 metres with 0.9 to 1 metre of barite-calcite-quartz separated by 1 to 2 metres of sheared chloritic, calcareous red volcanic. This vein has been traced for roughly 60 metres uphill from the Mann vein. It carries generally sparse sphalerite with minor chalcopyrite, bornite and tetrahedrite. At its most westerly exposure, coarse bornite, chalcopyrite and tetrahedrite occur with barite in a vein approximately 0.5 metre wide. Near the Mann vein, an unidentified green mineral in the WoMann vein may be smithsonite.
The Waterfall and Fault Breccia zones consist of remobilized gangue and sulfide mineralization from the veins into post-mineral fault zones. The zones consist of 30 to 40 per cent vein material filling spaces and voids created by fracturing over widths up to 1 to 2 metres. Clasts of mineralized vein may be up to 6 centimetres in diametre. These zones appear to be restricted to the hanging wall side of nearby mineralized zones and seem to have strike lengths less than 30 metres. The Fault Breccia zone is immediately above the High Grade Zone while the Waterfall zone appears above the Franmar zone.
The Crackle Breccia zone consists of a stockwork carrying barite-quartz-calcite veins and veinlets sparsely mineralized with sphalerite and minor galena and chalcopyrite. The zone strikes approximately 220 degrees azimuth and varies from over 8 up to 14 metres in width. It is just south of the Mann adit and appears to strike into the Mann vein. It has been exposed over a strike length of only 30 metres. The barite-quartz-calcite appears to form about 25 per cent of the overall zone. Locally, minor quartz veinlets contain a black, platy mineral occurring as fine 1 to 2 millimetre grains.
In a 2006 diamond drilling program, best silver values were obtained on the High Grade vein in DDH-MB-2006-10 which yielded 5.18 metres of 5258.0 grams per tonne silver, 0.66 per cent copper, 0.05 per cent lead and 0.05 per cent zinc; and DDH-MB-2006-19 which yielded 6.10 metres of 2260.0 grams per tonne silver, 0.404 per cent copper, 0.48 per cent lead and 0.56 per cent zinc. Best drill results on the Mann vein yielded 7.01 metres of 281.7 grams per tonne silver, 0.03 per cent copper, 0.28 per cent lead and 0.52 per cent zinc (Assessment Report 29066).
In 1902, the American Girl group (American Girl, Mountain Boy, Northern Belle and Hard Money) was staked. Some tunnelling was done on the American Girl claim from 1903 to 1905. From 1909 to 1914, Sir Donald Mann optioned the property and his company, Pacific Coast Exploration Co., conducted further tunnelling (on the Mann or No. 1 vein) and discovered a silver-rich boulder. The Mountain Boy Mining Company Limited was formed in 1910(?).
In 1927, W. Tolin optioned the property and the Pat Daly Mining Company was organized to develop the property. The following year the High Grade (or No. 2) vein was discovered as the source of the high-grade float. From 1928 to 1930, the Daly and Fagan tunnels were driven on the High Grade vein on the Mountain Boy claim and the Tolin tunnel was driven below the Mann tunnel on the Mann vein on the American Girl claim. In 1929, a shipment of about 4 tonnes of hand-sorted material produced 124,352 grams of silver, 154 kilograms of copper, 61 kilograms of lead and 80 kilograms of zinc (Property File - Mathews, 1942).
From 1936 to 1945, work comprised mainly prospecting, although some drifting and crosscutting was done. In 1936, 4 tonnes produced 77,726 grams of silver, 95 kilograms of copper and 125 kilograms of lead. It is possible that the production recorded for 1937 includes the production listed for 1936. In 1937, four shipments, totalling 38.1 tonnes, produced 743,455 grams of silver, 1334 kilograms of copper and 1525 kilograms of lead. In 1938, nine tonnes produced 74,959 grams of silver and 160 kilograms of copper. A shipment of 2.8 tonnes, which assayed 3.1 grams per tonne gold, 8553 grams per tonne silver, 2.2 per cent copper, 4.9 per cent lead, 5.8 per cent zinc and 0.4 per cent antimony, was sent to the Prince Rupert sampling plant in 1940 (Minister of Mines Annual Report 1940, page A42).
In 1974, the claims reverted to the Crown and, in 1976, R. Schumacher carried out underground sampling on the Mann tunnel.
In 1978, Northern Lights Resources Ltd. reportedly drilled one hole but there is no record of this work. In 1980, Pride Resources Ltd. acquired the property, including the surrounding Crown-granted claims, and conducted prospecting and a survey for an access route.
In late 1983, Pride Resources Ltd. carried out a prospecting, sampling and diamond-drilling program supported by helicopter from Stewart. Surface exposures of the High Grade Vein in the vicinity of the Daly and Fagan adits were sampled. The underground exposures of the Mann orebody in the Mann adit were sampled. Three short diamond drill holes were put down at the portal of the Mann adit to test the extent of the ore below the surface exposure.
In 1998, Ranmar Ventures Ltd. optioned the property from Minvita Enterprises Ltd. A 4.6 metre wide structure north of the Daly Tunnel contains high grade silver, up to 29,600 grams per tonne in grab samples (George Cross News Letter No.140 (July 22), 1998). During 1999, an exploration program including mapping of the veins, underground sampling, preliminary geological mapping of the rocks and trenching was completed. In addition, this program included trail and road building, bulk sampling and locating all previous adits as well as clearing of all located portal areas. Based on high silver assays from the High Grade vein, a 13.6 tonne (15 ton) sample was extracted from the High Grade vein during 1999 and shipped to the Cominco smelter at Trail, B.C. Sampling of the bulk sample by Mountain Boy Minerals indicated a grade of 15,920 grams per tonne silver, 2.14 per cent copper and 2.45 per cent lead; results from the smelter indicate a value of 18,854-grams per tonne silver, 1.1 per cent zinc and 2.5 per cent lead (Assessment Report 36417).
In 2000, an exploration including with minor surface sampling and diamond drilling was completed. Two BTW drill holes totaling 268.3 metres, one located at the Cameron portal was designed to intersect an off-shoot of the Mann vein and the other on the east side of the 4-Bees vein were completed. Because of the flat westerly dip of both holes, neither hit the intended target. Encouraged by the high grading results in 1999, Mountain Boy Minerals extracted 38 tonnes of hand-cobbed mineralization in 2000 and shipped to the smelter.
Mountain Boy Minerals acquired the property in 2005 and conducted drilling in 2006 and 2007. During 2006, an exploration program on the Mountain Boy and Hard Money claims in the central portion of the property consisting of pad construction and diamond drilling to test the silver tenor of the No. 3, High Grade and Mann veins. During the 2006 exploration program, 19 diamond-drill holes totalling 888.40 metres of BTW size drilling were completed from three different drill pad sites.
In 2011, a total of 2381.21 metres of btw diamond drilling was completed in 36 holes from 3 different pads. Some of the better intersections were 396.33 grams per tonne silver over 4.57 metres in DDH-MB-2011-1 and 4.42 metres of 117.98 grams per tonne silver in DDH-MB-2011-9 in the Mann zone. Low silver values were intersected in the splay zones.
In 2016, Mountain Boy collected a total of 33 rock samples of which 30 were bedrock and 3 were float. Samples were collected from the hanging wall areas of the Mann and High Grade vein areas.
In 2017, Mountain Boy Minerals sampled several chalcopyrite rich structures located west and above the previously explored high-grade vein on its MB Silver project. Samples were collected from two different zones located several hundred metres apart during this sampling program.