Mother Lode Mine, Deadwood Camp, Greenwood Mining Division, British Columbia, Canadai

Regional Level Types
Mother Lode Mine	Mine (Abandoned)
Deadwood Camp	- not defined -
Greenwood Mining Division	Division
British Columbia	Province
Canada	Country

The previously producing Mother Lode mine, along with its nearby companion the Sunset Mine, lies just north of Deadwood Creek in the so-called Deadwood Camp, about 4 kilometres north-west of the city of Greenwood, British Columbia, in the Greenwood Mining Division. Note that the spelling Motherlode, often encountered in the literature, is not correct; the legal name is Mother Lode.
There is a description of the property, including information on the Sunset Mine, on the British Columbia “Minfile” site, current to 2020. Portions relative to geology are quoted below:
“The property comprising the Mother Lode (Lot 704) and Sunset (Lot 788) (082ESE035) mines is centered four kilometres northwest of Greenwood at the elevation of 1050 metres. Access is by good gravel road which connects the property to the Mother Lode Creek road and Greenwood. The Greyhound (082ESE050) claim lies 1700 metres to the southeast.
Copper and iron-skarn mineralization occurs at several locations in the Greenwood mining camp. The skarn deposits are associated with the Upper Paleozoic Knob Hill Group and the unconformably overlying rocks of the Triassic Brooklyn Group [sic - Formation]. The Tertiary Penticton and Marron groups consisting of volcaniclastic and flow rocks unconformably overlie the Knob Hill and Brooklyn rocks.
The Knob Hill Group consists of massive chert, greenstone and amphibolite with minor pods and thin, widely scattered beds of limestone and argillite. The Brooklyn Group [sic - Formation] includes thick units of sharpstone [see comment in rock descriptions for the origin of this word] conglomerate and limestone, as well as thinner beds of siltstone, sandstone and calcareous chert-pebble conglomerate. The sharpstone conglomerate contains angular fragments of chert and minor limestone, greenstone and jasper clasts set in a fine-grained chert, calcite and chlorite-rich matrix. The conglomerate is massive near its base and commonly bedded near its top, with numerous interbeds of sandstone, shale, siltstone and minor limestone. The conglomerate is overlain by the Brooklyn limestone which reaches 350 metres in thickness and comprises limestone and minor siltstone.”
“The formation of skarn in the district appears to be preferentially controlled by the contact between Brooklyn limestone and underlying sharpstone and siltstone beds. The largest and most productive precious metal enriched (PME) copper skarns are in the lower part of the Brooklyn Formation, either in the transition zone between the lower sharpstone and the Brooklyn limestone, or within the Brooklyn limestone itself.
The copper skarn mineralization at the Mother Lode pit occurs in the same member of the Brooklyn Formation as the skarns at the Phoenix mine (082ESE020). The protolith is believed to be mainly sharpstone conglomerate, calcareous siltstone and limestone. The formation, which strikes northwards and dips steeply east, also includes a lower sharpstone conglomerate overlain by skarn-altered siltstone and lenses of Brooklyn limestone and an overlying fine-grained sharpstone. These stratified rocks are cut by slightly skarn-altered granodiorite and feldspar porphyry (quartz syenite) dykes from several centimetres to 30 metres wide. These dykes are found at all levels of the mine from surface down to the 152 metre level.
Skarn alteration of limestone and sharpstone conglomerate is fairly extensive. The limestone is mostly altered to garnet skarn, but banded garnet-epidote-actinolite skarn is also common. In the sharpstone conglomerate, the original chert pebbles are replaced by recrystallized strained quartz, while the volcanic fragments are partially replaced by epidote, garnet, magnetite and minor sulphides.
The ore at the Mother Lode mine consists of many lenses, pods and irregular zones of chalcopyrite, pyrite and magnetite as grains, aggregates and thread-like streaks and lenses, distributed in a gangue composed of varying proportions of actinolite, garnet, epidote, calcite and quartz. Chalcopyrite also occurs in larger and purer masses. Magnetite occurs in irregular masses and lenses of considerable size.”
Giles Peatfield comments:
The above quotes give a comprehensive outline of the geology and mineralization at Mother Lode and Sunset. For more details on mineralogy and especially rock types, refer to the comment sections below. Note that while the Minfile account mentions “Copper and iron-skarn mineralization . . . .”, the mines of the district were definitely copper producers with important precious metal credits – iron in the form of magnetite or hematite was of little importance.
It is difficult to provide a concise figure (or figures) for total production from the Mother Lode mine. There were two periods of production from the Mother Lode mine (1900-1920 and 1957-1962); the Sunset mine operated from 1900-1918. In the early period of operation at both mines, ore was transported by rail to the British Columbia Copper Company (later the Canada Copper Corporation) smelter at Greenwood (Wilson, 1913). The second phase of mining at Mother Lode saw an on-site mill producing a copper concentrate that was shipped at least in part to the Asarco smelter at Tacoma, Washington; the records are not fully clear.
The official British Columbia records show that from 1900-1920, Mother Lode shipped about 3.42 million tonnes of ore to the Greenwood smelter; recovered grades are calculated as 0.93 percent copper, 1.45 grams per tonne gold and 5.75 grams per tonne silver. During the same period Sunset shipped about 109 thousand tonnes to the same smelter; recovered grades are calculated as 0.79 percent copper, 1.32 grams per tonne gold and 6.83 grams per tonne silver. It is not fully clear from the records, but one assumes that these grades are based on sampling at the smelter.
For the period 1957-1962, a mill was erected at Mother Lode and a total of about 584 thousand tonnes of ore was milled. Recovered grades are calculated as 0.53 percent copper, 0.74 gram per tonne gold and 2.96 grams per tonne silver.
This was not a large mining complex in modern terms, but in the day it was the principal source of ore for the Greenwood smelter, although other mines in the area contributed lesser amounts. The main point to make is that the ore was direct-shipping, and was essentially self-fluxing, with the addition of small amounts of specialty ores from other district mines for fluxing purposes.
Giles Peatfield comments on the minerals reported:
The Mother Lode and Sunset mines have a relatively simple mineralogy, but with several points of interest. Some workers had the benefit of thin section analyses; others used field methods of identification that may in some cases be suspect. I have chosen to comment on all the minerals reported over the years, providing some details where appropriate:
Actinolite: Brock (1906) mentioned actinolite at both the Mother Lode and Sunset mines. LeRoy (1913) provided much more detail, noting that it was “. . . the best developed and most widely distributed gangue mineral.” It occurs in acicular and lath-like forms, sheaf-like and radiate clusters, or felty masses. Further, LeRoy stated that “Along some of the larger shear zones the actinolite has been converted into a substance resembling ‘mountain leather’ consisting of series of interlacing flat thin leaves and fibres, pale grey in colour but lacking the quality of toughness.” Olson and Sutherland Brown (1969) described “banded epidote-actinolite-garnet skarns”.
Arsenopyrite: Brock (1906) reported traces of arsenopyrite, and LeRoy (1913) made reference to this identification, but it has not been subsequently reported.
Azurite: LeRoy (1913) stated that “Azurite and malachite were found in the surface zone of oxidation.” No-one else has specifically mentioned azurite.
Biotite?: Fyles (1985) reported biotite as a component of the skarns, but gave no specific data, and the mineral has not been reported by other workers.
Calcite: This is common, as a component of the limestone units and in veinlets within the skarns. LeRoy (1913) mentioned that “. . . it occurs in irregular areas in the lime silicates, as veinlets traversing them, and as the cement in zones of brecciation. It is usually associated with quartz and also with the sulphide minerals. It has been known to occur in a very pure state, and some excellent crystals of Iceland spar have been found in the Mother Lode mine.”
Chalcopyrite: This is the principal copper mineral at Mother Lode, and occurs as both disseminations and more massive lenses.
Chlorite: LeRoy (1913) reported chlorite as an alteration product of garnet and as a breakdown of actinolite. Olson and Sutherland Brown (1969) mentioned chlorite after amphibole. In neither case were more particulars given.
Diopside?: The only mention of diopside at this locality is in the label description of a museum specimen – see note below for magnetite.
Electrum?: Timm (1936) reported that “. . . the Sunset sample contains rare sphalerite, and an unknown mineral, tentatively identified as electrum (gold-silver alloy).”
Epidote: This is common, reported by most workers. See also note below for magnetite.
Feldspar group: The only specific references to feldspars were by Olson and Sutherland Brown (1969), who described plagioclase (An40-50) and perthite. Other species are no doubt present.
Galena: This is not common here. Brock (1906) described an area in the Mother Lode underground workings, in what was probably skarn, as follows: “Near the wall in the 200 feet level, this ore has some argentiferous galena and blende.” LeRoy (1913) quoted this reference, but gave no further data. It is likely that this was a relatively isolated occurrence, as no subsequent workers have reported galena.
Garnet group: Garnet is common in the Mother Lode and Sunset ores, but specific data are scarce. LeRoy (1913) described the garnets at Mother Lode as andradite, but others have simply reported garnet.
Hematite: Timm (1936) reported a small amount of hematite in polished sections, with magnetite, pyrite and chalcopyrite. Brock (1906) reported that “No specular hematite has been found.” – see note below for magnetite. LeRoy (1913) made the point that the Mother Lode and Sunset ores differed from those in the Phoenix area, where in a similar geologic setting hematite was common.
Hornblende: Olson and Sutherland Brown (1969) identified hornblende in the granodiorite intrusive rock.
Limonite: This is no doubt common, derived from the oxidation of pyrite, but apart from LeRoy (1913) no workers have mentioned it specifically.
Magnetite: This is a common mineral at both mines, often in large masses. Brock (1906) reported that at the Sunset mine “The magnetite sometimes occurs in rosette-like aggregates resembling hematite.” This leads to an interesting point. The Pacific Museum of Earth at the University of British Columbia has a specimen (# 6849) with a label that describes the specimen as “hematite, with diopside, andradite” from the mine dump at the Motherlode [sic - Mother Lode], Greenwood. Given the Brock (1906) reference, I contacted Dr. Kirsten Hodge at the Museum and she replied by email on 15 June 2023. Her comment was “I would say it is definitely magnetite.” Note also that this is the only reference to diopside at this site. Further to this, Mark Mauthner, in emails to me on June 29, 2023 made the comment that his identifications were visual only, and that he was not aware of the Brock (1906) reference. Furthermore, he did not know how ‘diopside’ came to be mentioned – his comment was “It’s not on my original label.” He is of the opinion that it is actually epidote.
Malachite: LeRoy (1913) stated that “Azurite and malachite were found in the surface zone of oxidation.” Fyles (1985) reported “copper stain”, by which he presumably meant malachite and perhaps azurite.
Pyrite: This is commonly reported, from both intrusive rocks and skarns, but does not appear to be a major constituent of the skarns.
Pyrrhotite: This is reported by Brock (1906), and by LeRoy (1913) from the Sunset mine (quoting Brock), but is not of major importance.
Quartz: Quartz is common but not of particular importance. See the note above for calcite.
Sericite: Olson and Sutherland Brown (1969), describing the granodiorite intrusive rocks, mentioned that the plagioclase feldspars are partially sericitized.
Sphalerite: Brock (1906) noted that the ores contained a small amount of “zincblende”, (see note above for galena), and LeRoy (1913) quoted this reference. Timm (1936) mentioned rare sphalerite in a polished section of ore from the Sunset mine.
Titanite: Olson and Sutherland Brown (1969) reported that the granodiorite contains minor amounts of ‘sphene’.
Tremolite: LeRoy (1913) mentioned that tremolite, seen in thin section, was rare at this locality, occurring as “. . . sheaf-like aggregates associated with other gangue minerals.”
Zoisite: Reported by LeRoy (1913), in thin section. He commented that “It is colourless, and occurs in minute crystals and grains associated with epidote.”
Giles Peatfield comments on the rock types reported:
The various rock types reported for the Mother Lode – Sunset area have been described and named by various workers, ranging from Brock (1906) through LeRoy (1913), to Olson and Sutherland Brown (1969) and Fyles (1985), among others. Most of the rock type names are straightforward; the list is mostly from Fyles (1985). However, some require detailed explanation, as provided below:
Chert: LeRoy (1913) described “chert-tuff”, but much of this may have been conglomerate (q.v.). Olson and Sutherland Brown mapped chert on Deadwood Creek, south of the Mother Lode pit and to the east of a fault immediately east of the Sunset Mine. They made the point that these rocks were part of the older Knob Hill strata, in fault contact with the chert pebble conglomerates of the Triassic Brooklyn Formation. Fyles (1985) mapped cherts and chert breccias. He was uncertain of the age and stratigraphic position of these rocks, but allowed as they might in part be placed in the Brooklyn Formation. Again, see the discussion below re conglomerate.
Conglomerate: This requires considerable explanation. Brock (1906) did not specifically describe conglomerate, but he did mention that the footwall rocks of the Sunset Mine were altered to almost pure silica. He thought these might have been greenstone tuff or argillite, writing that “In places it is brecciated; the pebble-like fragments are embedded in serpentinous matrix.” LeRoy (1912, 1913) described rocks that he called “jasperoid” or “chert-tuff”, which he presumed to have been formed by silicification of pre-existing limestone strata. Newell (1969) provided an interesting summary of this problem, writing that “The Phoenix sharpstone conglomerate is another rock type which has been the subject of controversy over the years. Early writers (Brock, LeRoy) classified the rock as a ‘jasperoid’ and postulated derivation from limestone by a process of silicification. The calcareous matrix was believed to represent unaltered rock, the ‘fragments’, the products of hydrothermal processes related to ore formation. It is interesting to note that both LeRoy’s memoirs make note of the fact that ‘in the field the rock often simulates in appearance that of a breccia or conglomerate.’ To make this observation and then suggest a hydrothermal origin for a stratigraphic unit of broad extent must have constituted a formidable feat of mental gymnastics.” What is even more interesting is that in LeRoy’s earlier work (1909) in the Phoenix area, he described three stratigraphic assemblages, of which the middle one, based on his description, clearly includes the Brooklyn Formation as later defined. In this report, LeRoy (1909) described the rocks as “. . . quartz breccias and conglomerates derived from the lower series, siliceous, chloritic and feldspathic tuffs and crystalline limestones”. And yet, shortly thereafter, LeRoy (1912) has made these conglomerates into “jasperoids”. Seraphim (1956, 1957) was the first to clearly demonstrate that the rock is a conglomerate, of regional extent, within the Brooklyn Formation; he appears to have been the first to use the term “sharpstone”, describing it in his 1956 paper as “A conglomerate formed from stones predominantly angular.” Later workers (Olson and Sutherland Brown (1969); Peatfield (1978) and Fyles (1985), among with many others, have clearly recognized these rocks, along with limestones, marbles and some finer-grained sedimentary strata, as comprising a regionally extensive stratigraphic unit, cropping out discontinuously for over 50 kilometres. Throughout the Boundary District, the conglomerates are usually called ‘sharpstone conglomerates’. For some inexplicable reason, Church (1985, 1986) chose to elevate the Brooklyn Formation to Group status, although it had been clearly stated by Peatfield (1978) that “The Brooklyn Formation is a mappable, heterogeneous unit, consisting of a large number of rock types which lack lateral continuity. A distinctive feature of the formation is this internal heterogeneity.” This is in agreement with the provisions Article 24, (b) of the North American Stratigraphic Code (AAPG, 2005). Fortunately, subsequent workers, e.g. Fyles (1985) and Tempelman-Kluit (1989) did not follow Church’s lead, and continued to use “Brooklyn Formation”, although the error persists in the Minfile description – see quote above.
Limestone: Brock (1906) simply reported limestone, with no particular description. LeRoy (1913) described the limestone as “crystalline”. Olson and Sutherland Brown (1969) simply reported “limestone” with no qualifications. Fyles (1985) reported both crystalline limestone and marble.
Quartz syenite: This is another rock with a chequered history in the area. A very early reference to the Tertiary aged alkaline dykes and lavas in the region was by Brock (1906), who described the dyke rock at Mother Lode as “alkali-syenite porphyry”, which he compared (p. 104A) to the “Rossland syenite” of the West Kootenay district and called “pulaskite”. The rock was described in detail by Daly (1912); the rock name has become widely used in the area up to the present time. This rock name was originally used by Williams (1891) to describe a nepheline-bearing syenite from Pulaski County, Arkansas. Unfortunately, the rocks in the Boundary District do not in all cases contain nepheline, and some, such as at the Mother Lode, have small amounts of interstitial quartz, as noted by Olson and Sutherland Brown (1969), who wrote that “These rocks, locally called pulaskites, are quartz syenites . . . .” It is instructive to note Jackson’s (1997) definition of pulaskite: “A light-colored, feldspathoid-bearing, granular or trachytoid alkali syenite . . . . The term has also been applied to quartz-bearing syenites. The name, given by Williams in 1891, is from Pulaski County, Arkansas. Not recommended usage.” The name pulaskite has been used by, inter alia: LeRoy (1909, 1912, 1913); Seraphim (1956, 1957); Little and Thorpe, (1965); Little and Monger (1966); Church (1985, 1986); and Fyles (1985, 1990). However, Monger (1968) had remarked that the syenite porphyry in the Greenwood area in most cases contains minor amounts of quartz, and that “The ‘pulaskite’ or alkaline syenite of Daly (1912, pp. 417-418) and LeRoy (1912, pp. 49-52) is merely a variety of the above syenite, characterized by its aphanitic fawn to buff matrix, and appears to occur only in the smallest intrusive bodies.” Little (1983) came to the same conclusion, noting that in some places the dyke rocks contained nepheline and in others did not. How one wishes that subsequent writers had taken this into account!
Skarn: At the Mother Lode and Sunset mines, and at other mines in the “Boundary District”, skarn is used in a way reminiscent of the old Fennoscandian usage; Holmes (1965, p. 172) wrote that the name is “. . . from a Swedish word for rubbish, the implication being that the silicate minerals are merely so much waste in quarries that are being worked for limestone.” Modern usage, especially by American geologists, implies metasomatism, with introduction of various elements such as Si, Al, Fe and Mg. Evidence from Mother Lode and Sunset mines, and from others in the Boundary district strongly suggests that there has been little or no introduction of these elements from igneous sources, and that the skarn minerals have been formed by metamorphism, probably thermal, of constituents of the original sedimentary rocks (see Peatfield, 1978 for a more detailed discussion). These rocks would be better called exoskarns, following the usage of Jackson (1997).

Giles Peatfield
BASc. (Geological Engineering) University of British Columbia 1966.
PhD Queen's University at Kingston 1978.
Worked for Texas Gulf Sulphur / Texas Gulf Inc. / Kidd Creek Mines - 1966 to 1985.
Vancouver based consultant 1982 to retirement in 2016.

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Link to British Columbia Minfile:	082ESE034

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References