Virtual Museum ID: 19-AME42
This allemontite (stibarsen) sample comes from the Engineer Gold Mine near Atlin Lake, B.C. You may notice that the mineral has two different names and while both are accepted stibarsen is the official accepted name.
It is a mineral composed of Arsenic and Antimony and is white to reddish-grey, and it tarnishes to grey. This is one of the minerals that make it more difficult to process ore from mines because of Arsenic's toxicity to living organisms. While some animals need trace amounts of arsenic in their diet, it is highly toxic in large amounts to most living organisms. When mining deposits that have high levels of Arsenic, mining companies must pay special attention to keeping it contained.
The Engineer Mine is in Northwest B.C. with in the vicinity of Atlin, B.C. It operated as an underground Gold mine that eventually turned into a fully serviced town. The first hint of Gold was discovered in 1899 by Swedish prospectors. Later on an engineer discovered visible Gold in quartz/calcite veins and staked the claims with the Engineer Mining Company. It was finally mined in 1924 after being transferred to a New York ownership group. Overall by 1952 over 5.5km of underground tunnels had been created at the mine site and almost 20,000 oz of gold had been recovered.
The Engineer Mine is known for its excellent visible Gold samples hosted in quartz-calcite-pyrite veins and hydrothermal breccias. It has excellent examples of high grade Gold and Silver mineralization.
The information listed below relates to the current holding location or collection that the sample is from, and whether the item is viewable at that location or is part of a private collection. Coordinates are given as guides, and we remind you that collecting specimens from these locations is not allowed. Caution is advised visiting such sites and Below BC assumes no responsibility for any injuries or trespassing charges that may occur as a result of the viewer entering these sites.
Original Collection:Association for Mineral Exploration (AME)
Virtual Museum ID:19-AME42
Date Added to VM:2018-02-15
Sample Origin:Atlin Lake, B.C.
Specific Site:Engineer Gold Mine
Datum:08 (NAD 83)
Primary Mineral Formula:SbAs
Advanced Geological Information
The following section provides geological data relating to the specimen or the site it was collected from, when available. Information has been obtained from various sources including private and government datasets but may not be up to date. Any geological time periods or ages listed often relate to the primary geology of the area, and may not be the actual date of an event such as mineral formation.
Geological Period:Lower Jurassic
Stratigraphic Age:178.9 to 185.6 Million Years
Minfile ID:104M 014
The Engineer mine is located on the east side of Tagish Lake about 15 kilometres south of Graham Inlet and 30 kilometres west of Atlin. The property was discovered in 1899 and operated for 3 years. Underground work and production then took place from 1910 to 1918, from 1922 to 1928, during the summer only from 1929 to 1930, and hand mined from 1932 to 1934. Minor production (stockpile?) is recorded for 1944 to 1946, 1949 and 1952. Sporadic work occurred in 1948, 1952, 1962, 1982 to 1983 and in 1987 (by Total Erickson). See below for detailed property history.
The mine is associated with several vertical, northeast striking quartz-calcite veins hosted in well bedded sediments of the Lower Jurassic Laberge Group. Shale, siltstone, and greywacke show excellent graded bedding, load casts, flame structures and contain rare ammonites and other fossil debris. Regional bedding strikes northwest and dips moderately northeast. Isoclinal folds are orientated northwest parallel to the main shear zones which run through the property. The veins are perpendicular to these structures and discordant to bedding. A second phase of buckling occurred perpendicular to the first phase. "Quartz hubs" or zones of massive bull quartz occur where the ore-producing veins intersect the shear zones, although these "hubs" are barren.
The Engineer mine quartz veins are narrow, less than 2 metres wide, but have consistent orientations. Ore grades however, are very sporadic ranging from trace to 50 grams per tonne gold. Native gold is the main metallic mineral and occurs in pockets. Minor pyrite, tetrahedrite, chalcopyrite, mariposite, antimony, berthierite, and tellurides are also reported. Veins are very vuggy with many open-space textures which exhibit very "clean" contacts with the hostrock and commonly graphitic banding. The Double Decker and Engineer veins lie to the southwest of the shear zone and the Boulder vein lies to the northeast. The Engineer and Double Decker veins have been most extensively developed.
The Engineer Mine is considered to be a transitional epi-mesothermal deposit (Bulletin 105, pages 168-167). Features that support this transitional classification include a lower than usual silver/gold ratio (0.5 to 1- typical of mesothermal values) combined with depositional features indicative of open-space filling and episodic filling and other shallow features. The ore grade vein material shows vuggy and drusy millimetre-long quartz crystals ranging from green to blue to brown, and abundant cockscomb and colloform textures in successive layers quartz and calcite coating country rock fragments and vein material.
The claims in the area were staked in 1899 by men working on the construction of the White Pass and Yukon Railway. The Engineer Mining Company of Skagway was formed to explore and develop the outcropping of auriferous veins which led to the original staking. In the period from 1900 to 1902 a number of surface cuts and adits were completed. A small amount of hand-sorted ore was shipped and a stamp mill was brought onto the property. However, there are no reports of the mill being used during this period. The first interest in the property by the original owners waned and the claims lapsed in 1906. Edwin Brown and partners of Atlin restaked the ground and sold it to the Northern Partnership syndicate of Atlin, headed by Captain James Alexander, in 1907. From 1908 to 1911 this syndicate carried out extensive surface exploration and mining and the stamp mill brought to the property earlier was set up.
In 1912, James Alexander increased his control of the property and started a major underground development. Most of this development was on the Engineer vein. By 1918, a 64 metre shaft was sunk and four levels developed on the vein. As well, a crosscut (Mill crosscut or 500 level) from near the lakeshore was initiated and was intended to intersect the Engineer vein after 360 metres. It was undertaken to provide access and a haulage level for the Engineer vein and other parallel structures to a mill site about 30 metres above the lake. A crosscut from close to the 100 level portal was started to intersect the Boulder and neighbouring veins, though work on this heading did not progress very far. Production records are incomplete, but it appears that sporadic production of high grade ore was accomplished during this period. Annual production figures range from 31 to 998 tonnes, with grades consistently above 68.5 grams per tonne gold. The Minister of Mines Report for 1918 reports one 11.14 kilograms allotment of hand sorted ore contained 4977 grams of gold. In 1918, James Alexander lost his life in the sinking of the “Princess Sophia” in Lynn Canal, along with his wife, a mining engineer, and agents for a prospective buyer of the property. The property fell into litigation concerning ownership after the loss of Alexander and was idle until 1922.
In 1922, heirs of Alexander, the Smith interests, were awarded the property. From these people New York-based entrepreneurs acquired control of the property in 1923 and formed Engineer Gold Mines to develop it in 1924. Considerable work was undertaken from 1923 through 1925. New bunkhouses were constructed, a new 50 TPD mill constructed, a power dam and generating station were constructed on the Wann River south of the mine and a transmission line to the camp completed, the Mill crosscut was completed, and 3 diamond-drill holes were drilled to test the A and B hubs and a number of small veins by the Boulder vein. Up to 140 men were employed at one time. In 1925, reports from the mine were so favourable that stock of Engineer Gold Mines rose to $100.00 on the New York Exchange. Irregularities in the stock rise resulted in fraud investigation against some of the principals of the company. Reportedly more effort was put into stock manipulation by the owners than in developing mineable tonnage.
Between 1925 and 1927 the majority of the mine’s reported ore was produced. During this period 13,700 tonnes grading 26 grams per tonne gold were milled. Further development work during this time included the sinking of an internal shaft from the 500 level on the Engineer vein and the development of the 600, 700 and 800 levels on the vein 100 feet below each other. On the 800 level a crosscut to the Double Decker vein was completed and this vein drifted upon. On the 500 level a crosscut to the veins east of east of the A shear, (Boulder, Andy, Blue, Shaft), was driven and some drifting on these veins done, including 180 metres on the Boulder vein. As well a shaft was sunk on the B Hub and some drifting off the shaft undertaken. Incomplete production reports indicate that some production occurred from the lower mine levels and that good grade was encountered on the 800 level. Sporadic good values were reported from the Boulder vein as well.
Mining and production became sporadic after 1927 and less than 900 tonnes of ore were produced from 1928 to 1931 when the mill officially shut down. Some development continued to explore the lower grade, high tonnage targets along the A shear. Some low gold values were reported from the zone during this work.
From 1932 to 1934, Reginald Brooks did some selective hand mining on the property. In 1934, Mining Corporation of Canada bought the mine at a sheriff’s sale. They never worked the property, but lessees from Atlin intermittently high graded from the Engineer and Double Decker veins above the flooded 600 level until 1952.
No production was reported after 1952. Production records are incomplete but from 1910 to 1952, 16,700 tonnes of ore resulting in 611 kilograms of gold were reported (37 grams per tonne gold). During this period some 5500 metres of drifting and crosscutting were completed. Production was carried out from eight levels on the Engineer vein, (over a vertical distance of 190 metres), from two levels on the Double Decker vein, and from a number of surface cuts.
In the early 1960s, Tagish Gold Mines Ltd. acquired the five main Crown grants of the old Engineer mine. In 1975, Nu Energy Development Corporation acquired the mine through a merger with Tagish Gold Mines. Nu Energy conducted an underground program in 1975 involving detailed sampling of the A shear zone where it is crossed on the 500 level, some underground mapping, and an attempt to dewater the mine to resample levels below the 500 level. Gold assay results from percussion drill sludges and chip samples of the backs within the A shear on the 500 level were very low. Most were 0.34 gram per tonne gold to trace and none were higher than 1.0 gram per tonne. Attempts to dewater the lower levels were unsuccessful and only a brief look at the 600 and 700 levels was accomplished. Unexpectedly high water inflow rates exceeded the capacity of the pumps used.
In 1979, Nu-Lady Gold Mines Ltd. optioned the Engineer mine. In 1980, this company conducted a 15 hole diamond drilling program targeted on known vein structures accessible from the main mine. No significant intersections resulted. In 1981, a further 11 holes were drilled and a geochemical soil survey conducted over an overburden covered area in the north part of the property. Six of the holes tested northeastward extensions of the Double Decker and Engineer veins. Three holes were drilled by the Boulder vein east of the A shear and two holes were drilled to test an anomaly generated by the soil geochemical survey. Only one hole, 81-11, testing the geochemical anomaly, had a significant intersection. It had one assay of 6.5 grams per tonne gold across 0.76 metre.
In 1983, further work discovered the Nutcracker vein 45 metres southeast and parallel to the Engineer vein. The vein was 0.4 metre wide where discovered and a composite grab ran 103 grams per tonne gold. The structure was trenched but was only 1 to 5 centimetre wide over a 12 metre strike length and the original 0.4 metre appears to have only been a small pod. Six drillholes were targeted on the structure but only stringers with low gold values (highest grade 0.82 gram per tonne gold) were encountered. One other hole was drilled in 1983 but no information is available about it. Nu-Lady's option on the property lapsed in 1985. Core from their drill programs was put into new core racks during 1987 and boxes re-labeled where possible. Unfortunately drill plans for the 1980 holes and all drill logs are unavailable.
In 1987 Erickson Gold Mining Corp. (Erickson) became the owner of the property by takeover of Nu Energy. Early in that same year they flew an airborne VLF/Mag survey, before increasing the property size by staking, and then doing ground geophysics, surface geological mapping and sampling and soil geochemistry over the old mine site, and some of the new claims. During fall of the same year, a diamond drilling program consisting of 1,178 metres in eight holes followed up on the earlier work, and tested known structures at depth.
In 1989 Gentry Resources Ltd. optioned the property from Erickson and did magnetometer and VLFEM surveys over the Erickson grid. In 1990 Gentry Resources Ltd and Winslow Gold Corp acquired the property from Erickson by a share agreement. Prior to the 1992 season Ampex Mining negotiated a letter of intent with the new owners and early in that year made an initial assessment of the condition of the underground workings. In June of 1993 Ampex and Gentry/Winslow formed a formal pre-production agreement, and subsequent to that Winslow acquired all of the property from Gentry. In July 1994 Ampex agreed to sell all of its interest to the Old Engineer Mining Corp., which in November of 1997 changed its name to simply the Engineer Mining Corp (EMC).
During 1991 to 1992 the portal and most of 5 level was rehabilitated by Ampex. Blasting and sampling on the No. 2, No. 3, and Double Decker veins was unsuccessful in locating new gold mineralization. On the Engineer vein impressive samples of gold in roscoelite were collected on small remnants of an ore shoot found in pillars between surface and 2 level, and long the 5 level (bonanza shoot). In 1993 the northeast part of the mine was re-habilitated.
Estimated reserves in 1994 were 20,000 tonnes grading 34 grams per tonne gold (Information Circular 1994-1, page 19).
Ampex Mining, under an agreement with Winslow Gold Corporation, mined and milled approximately 345 tonnes of vein material from stopes on the Engineer and Double Decker veins during a bulk sampling program. Ampex installed tracks and mobilized equipment to improve mining efficiency. A further program of exploration, limited milling of material from near-surface veins and preparation for dewatering the lower levels on the Engineer vein is planned. The company hopes to bring the 27,500 to 45,300 tonnes of indicated reserves into the proven reserves category (Information Circular 1995-9, page 17).
In 1995, Ampex Mining carried out a program of test milling and underground rehabilitation and sampling with support from the Explore B.C. Program with a view of upgrading indicated reserves to the proven reserves category. Results of this program were not conclusive but encouraging and further sampling and dewatering of lower levels is planned (Explore B.C. Program 95/96 - M30).
In 2007 the Engineer crown grants were optioned by BCGold. In that year 160 rock samples were collected from underground, surface, and selected 1987 core.
In 2008, BC Gold exploration included mapping, petrology, underground chip/channel sampling, and drilling. Mapping at 1:500 scale was compiled for surface and 5 level at 1:1,500 and 1:1,000 scales respectively. Underground channel sill sampling with a diamond saw was done on the Shaft, Boulder (2 areas), Engineer, Double Decker (2 areas), and Shear A. The drilling (7 holes, 1,846 m) targeted the late stage hydrothermal breccia zone within a 400 m strike length of Shear Zone A.
No work was done on the property in 2009.
The 2010 work consisted of drilling thirteen HQ diamond drill holes (1,218 meters), in two phases, from two underground drill bays located on 5 level. From the first drill bay (the old hoist room) four holes targeted the Double Decker vein on 8 level in an area where 1928 reports indicated 84.35 grams per tonne gold were drifted on over the mined width of the drift for a 10.0 metre distance along the drift. An additional three holes drilled from the same drill bay targeted the Engineer vein at very low angles. The remaining 6 drill holes were drilled from a second drill bay located a further 30 metres along the main crosscut. These holes all targeted the Engineer vein down dip below the “bonanza shoot” between 5 and seven level where previous sampling had indicated sporadic high grades.
In May 2011 BCGold Corp. announced an updated Inferred resource estimate, which included the Engineer and Double Decker zones, of 41,000 tonnes grading 19.0 grams per tonne gold, calculated at 5 grams per tonne gold cut-off (Stockwatch News Release May 25, 2011). Totaling 14,000 tonnes averaging 52.5 grams per tonne Au at 25 grams per tonne cut-off. Six bulk samples totalling 300 tonnes were mined and milled from the Engineer and Decker veins. More than 600 metres were trenched on the Boulder, Shaft, Double Decker and Shear B zones, all of which were previously worked in the 1920s. Infrastructure upgrades include refurbishment of the 30 tonnes per day gravity mill circuit, shaft area refurbishment and dewatering. BCGold consolidated its land position around Engineer in 2010 by entering into an Option Agreement to acquire 100 per cent interest in five mineral claims adjacent and partially surrounding the Engineer property. Prospecting and geological mapping were conducted with the assistance of a 600 kilometre SkyTEM airborne geophysical survey.
Activities on site during 2012 included dewatering of levels 6 and 7 which have been submerged since mine closure in 1928. Ventilation and water services were restored allowing access to these levels. Geologists surveyed and sampled the down-plunge extent of the 505-3 and 505-5 gold shoots hosted within the Engineer Vein. One hundred ninety panel samples were collected along 74 metres of vein exposure on 6 Level and along 173 metres of vein exposure on 7 Level.
In 2013, BC Gold Corp signed a letter agreement with Blind Creek Resources to option mineral claims adjacent the Engineer mine. Several gold bearing structures extend from the Engineer mine onto the optioned claims and will be the focus of exploration activities planned for 2014. No ground work was carried out at the Engineer mine during 2013. In January 2013, BCGold Corp announced results of a Mobile Metal Ion (MMI) soil geochemistry survey in the Gold Hill (Happy Sullivan) area northeast of the Engineer mine (Press Release, January 8, 2013).
In 2014, a total of 55 soil samples and one rock sample were submitted for analysis by BC Gold in order to evaluate areas of the Engineer Mine property, especially along the gulley where Shear A extends toward the south. The program also tried to discern the usefulness of soil sampling compared to the data collected in previous soil and MMI surveys. The previous MMI was thought not to have worked any better than the 2014 soil survey. A discrete airborne magnetic anomaly which lies to the east of the Shear-A gully was thought to have resulted from a distinct phase of the Engineer stock.
In 2015, BCGold Corp. received the final research report on the geology and mineralogy of the bonanza-style gold veins at its Engineer mine property from Dr. Leo J. Millonig. Dr. Millonig stated: "The lower limit of the bonanza zone, i.e. the boiling horizon, has not been reached yet, and that the lower, less developed mine levels are likely to contain high-grade mineralization. This conclusion is supported by visible gold observed by the author on the seventh mine level (627 m el.), and results of geochemical assays from that level." (Stockwatch April 13, 2015).
Refer to Happy Sullivan (104M 013) for related details of work done on the Engineer property.