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Minerals of the Silvana mine, Sandon, British Columbia.

The Silvana mine has produced an array of very fine to spectacular micromineral and thumbnail specimens including rare, fiery-orange pyrostilpnite, lustrous cubanite, pyrargyrite and stephanite as well as showy, irridescent pyrrhotite.

INTRODUCTION

The Silvana mine is an amalgamation of many mines in the heart of the Slocan mining camp of British Columbia. It lies at the head of the east fork of Tributary Creek just south of the town of Sandon. Sandon is about 13 km (8 miles) east of New Denver on Highway 31A. National Topographic Series Map Sheet 82 F/14 covers this area.

HISTORY

The story of mining in the Slocan camp began when native peoples extracted lead from the rich galena veins to manufacture bullets in the mid to late 1800's. As prices for silver soared in the early 1890's, prospectors and miners rushed into the area. By 1892, 750 claims were recorded (Cairnes, 1934).

The first boom in the Slocan area began in 1891 with the discovery of the Payne claim. Prospectors Eli Carpenter and Jack Seaton were not having much luck that season. Finding the way back to Ainsworth Hot Springs through the dense bush in this steep, rugged terrain was proving to be difficult. They climbed Payne Ridge for a better view to orient themselves. At 2,100 meters (6,890 feet), the two came across a rusty ledge a few meters wide. Sampling uncovered rich veins of shiny galena.

After quickly staking the "Payne Claim," they hurried back to Ainsworth. Once there, Carpenter headed off to the assay office, Seaton was off to sate a thirst. Carpenter, a cunning, tight-lipped man, had admonished Seaton, a boisterous, care-free man, to keep the discovery quiet so they could return to look over the property more carefully. However, whiskey flowed in through Jack's lips and words flowed out. Before the end of the night the whole town had heard of the Payne discovery.

Carpenter returned from the assay office with a report showing silver values of 175 ounces per ton and 75% lead but told his partner loudly, "Our assay reads silver twenty-five ounces and not much lead either!" (May, 1986).

Carpenter then left, hooked up with a new partner, to sneak back to the property. Seaton learned of his plan and with four others struck out to beat Carpenter to the claim. This group, known as the "Noble Five," reached Payne Ridge first. They scouted around and staked another 21 claims, all of which became producing mines.

The first boom lasted until 1899. A major labor dispute in that year slowed production; it did not recover until the world war in 1914 when the demand for base metals increased.

This renewed prosperity continued until 1920, having reached its peak in 1918, when a combination of more strike action and declining market values for metals brought production to a halt. Hungry workers either left the area or trickled back to work. Production never reached prior levels and continued to fluctuate until 1929. As the economy bottomed out on Wall Street, so did mining in the Slocan area.

During the late 1940's, the Kelowna Exploration Company undertook a program of exploration and mapping that lasted until 1951. Silver Standard Mines continued exploration of the properties after acquiring an option on 59 claims in the vicinity in 1961. This exploration company and others formed the Silmonac Syndicate in 1962. A year later the Syndicate incorporated and became Silmonac Mines Limited. Exploration continued off and on until 1970, when it was determined that enough reserves existed to warrant commencement of production. Silmonac Mines had its name changed to Silvana Mines Incorporated in 1977 after a reorganization of the company. Dickenson Mines acquired the properties and operated the Silvana mine until 1989, when Treminco Resources Limited bought the property. The mine was closed in July of 1991 due to low base metal prices and low ore reserves.

GEOLOGY

The first geological map work was done in 1894 and 1895 by R. G. McConnell. Cairnes (1934) and Hedley (1952) wrote the two most significant general geological reports on the area. There are also several minor reports and papers dealing with this region that are not cited in this article. However, to provide a comprehensive list of references, they are mentioned in the reference section.

The Slocan mining camp lies within the Kootenay Arc, an arcuate zone of highly deformed Proterozoic to mid-Jurassic metasedimentary and metavolcanic rocks. It lies on the eastern edge of the Omenica Crystalline Belt and contains the suture zone between the amalgamated, allochthonous terranes and the ancient western margin of the North American craton (Price et al., 1981).

The orebodies of the Silvana mine lie within the Triassic Slocan Group, a thick succession of north-northwest-trending argillites, quartzites and limestones that appear to be folded about a large, recumbent syncline (Hedley, 1952). Apophyses thought to be related to the underlying Upper Cretaceous Nelson Batholith have intruded the Slocan Group. The ore occurs as lenses less than 2 meters thick with down-dip and strike lengths up to tens of meters within the Main Lode. The Main Lode is a south to southeasterly dipping zone of faulting and brecciation up to 50 meters (164 feet) wide and interpreted over 11 km (6.8 miles) between Silverton Creek and Sandon.

Sphalerite with gangue siderite and minor galena with variable silver values characterize the first phase of at least two stages in the main lead/zinc sulfide mineralization. Argentiferous galena characterizes the later mineralization phase. Later shearing is responsible for the extensive "graphitic" slickensiding throughout the Silvana portion of the Main Lode.

Remobilization of silver and other elements during this shearing produced the sulfide and sulfosalt minerals that occur in tension gashes along the slickensiding and cavities in the ore veins. Other minerals of interest to the collector occur in the calcite veins associated with the intrusives.

MINERALS

Acanthite AgS

Tiny ([greater than] 0.5 mm) black blades of acanthite associated with minor native silver in massive quartz were found on some specimens from the 4560 stope. However, these are suspected to be "cabinet growth" on samples left in storage for some time before being unwrapped and examined. Bladed acanthite was also found coating cubanite needles (D. K. Joyce, personal communication).

Anatase Ti[O.sub.2]

Anatase occurs as pale blue, brown or silver-gray crystals in quartz-lined fractures in the intrusive dikes on the 4270 level. The crystals are less than 1 mm long. The calcite-infilled fractures must be etched to expose the anatase.

Antimony Sb

Gwillam (1896) notes the occurrence of antimony in galena at the Alamo mine, which neighbors the present Silvana properties. Native antimony was found as tiny ([less than] 0.1 mm) blebs with boulangerite, freibergite and meneghinite in a polished section of the massive, sheared galena.

Aragonite CaC[O.sub.3]

Aragonite occurs as acicular white tufts, up to 2 or 3 mm in width, associated with gypsum, sulfosalts and pyrrhotite. Aragonite also occurs as an efflorescence on the walls in the mine.

Argentopyrite Ag[Fe.sub.2][S.sub.3]

This rare sulfide occurs as tiny prismatic pseudohexagonal crystals associated with polybasite, cubanite, pyrargyrite, pyrrhotite, calcite and aragonite in the 44-11-8 and 4560 stopes. Some elongate prisms show a star-shaped cross-section.

Needle-like crystals of a silver-iron sulfide suspected to be argentopyrite were discovered on a sample from the Silvana mine. Associated with these crystals are cubanite needles, some with silver-rich zones. Research is presently being conducted to determine whether or not argentopyrite and cubanite form a series.

Arsenopyrite FeAsS

Stope 40-13-1 produced some massive to subhedral arsenopyrite. This is noteworthy only because it shows the presence of arsenic in the system.

Barite BaS[O.sub.4]

Barite occurs as cream-white, tabular crystals up to 1 mm on an edge in the chlorite-coated extension fractures within the heavily slickensided shear zones. It is most often associated with pyrrhotite and quartz.

Boulangerite [Pb.sub.5][Sb.sub.4][S.sub.11]

Boulangerite occurs as hairlike tufts in vugs and as fibrous masses up to 1.5 cm long in the massive, sheared galena. Additional associated minerals include meneghinite, antimony, freibergite, sphalerite, siderite and quartz.

Calcite CaC[O.sub.3]

Calcite occurs as euhedral crystals of various habits throughout the mine. Typical habits include trigonal bipyramids, tabular, six-sided plates and hexagonal prisms with rhombohedral terminations. Crystals up to 4 cm in width have been found.

Chalcopyrite CuFe[S.sub.2]

Stope 45-13-0 produced lustrous disphenoids ([less than] 1 mm) intimately associated with sphalerite on gemmy clear quartz crystals. Clusters of lustrous disphenoids occur with pyrostilpnite, pyrargyrite, cubanite and quartz on specimens from the 42-12-1 stope. Chalcopyrite usually occurs as small (5-10 mm), massive blebs in sphalerite. These are uncommon except in the 43-13-2 and 43-13-3 stopes.

Cubanite Cu[Fe.sub.2][S.sub.3]

Lustrous cubanite crystals with an elongate, striated prismatic habit, originally thought to be a strange habit of chalcopyrite, occur associated with pyrrhotite, pyrargyrite, galena and pyrostilpnite in several stopes. Cubanite also occurs as single or small tufts of very fine, elastic needles up to 5 mm in length. As mentioned under Argentopyrite, some cubanite needles found on one sample contain silver-rich zones.

Dravite Na[Mg.sub.3][Al.sub.6][(B[O.sub.3]).sub.3][Si.sub.6][O.sub.18][(O H).sub.4]

Dravite occurs as greenish black needles in calcite-filled veinlets associated with intrusive dikes. The crystals are usually no more than 1 mm thick and up to 4 mm long.

Epsomite MgS[O.sub.4][center dot]7[H.sub.2]O

Epsomite occurs as white balls in fractures within the slickensided shear zones. These tight aggregates of bladed crystals occur with aragonite and are up to 2 mm wide. It is possible, since this mineral has been found only in older, mined out stopes, that the epsomite formed after mining activity.

Freibergite [(Ag,Cu,Fe).sub.12][(Sb,As).sub.4][S.sub.13]

Cairnes (1934) uses the term "gray copper" to describe occurrences of freibergite and tetrahedrite. This, he states, occurs as masses within the galena in several Sandon area mines. The report by Dubord also indicates the presence of tetrahedrite in polished sections of the massive ore. Freibergite was found as crystals in vugs and as blebs in massive, sheared galena specimens found in the millsite ore bin. All of the euhedral specimens originally labeled as tetrahedrite in the authors' collections, for which the source stopes were known, have been shown to be galena with an odd habit.

Galena PbS

Massive argentiferous galena comprises the main ore vein material. This vein material exhibits some interesting deformation textures. Of interest to the micromounter though, are the highly lustrous, euhedral crystals found in stopes 42-13-0, 42-13-1 and 42-13-8. Most of these crystals show cubic forms modified by octahedrons and occur up to 7 mm in size, though most are in the 0.5 to 2 mm range.

Gypsum CaS[O.sub.4]

Gypsum occurs as clear blades (1-2 mm) most often associated with aragonite on limonite-coated fracture surfaces in the 44-11-8 and 43-11-8 stopes. Stephanite and polybasite are also common associates. As with the aragonite, it is possible that some gypsum formed after mining activity in the stope.

Heulandite (Ca, [Na.sub.2])[Al.sub.2][Si.sub.7][O.sub.18][center dot]6[H.sub.2]O

Water-clear crystals of heulandite occur in a shear zone within the intrusions in the 4000 level, #4 West lateral drift. The crystals measure up to 1.5 mm in length and are associated with stilbite.

Laumontite Ca[Al.sub.2][Si.sub.4][O.sub.12][center dot]4[H.sub.2]O

When freshly exposed, laumontite occurs as clear, colorless prisms up to 3 mm in length. These, however, quickly alter and are usually milky white by the time the collector reaches the mine portal. After that, the laumontite is fairly stable. It occurs in a wide "graphitic" shear zone in the 44-11-1 stope.

Meneghinite [Pb.sub.13]Cu[Sb.sub.7][S.sub.24]

Some specimens of massive, sheared galena, picked up from the ore bin at the millsite, were found to have vugs lined with meneghinite crystals up to 2 mm in length. These are associated with crystals of galena, sphalerite, freibergite, boulangerite, quartz and siderite. They are elongate, heavily striated, sometimes curved prisms with sphenoidal terminations.

Orthoclase KAl[Si.sub.3][O.sub.8]

Gemmy, colorless crystals of orthoclase line calcite-filled veinlets in a porphyry on the 4755 level East. The crystals exhibit a prismatic habit with wedge-shaped terminations. Lustrous cubes of pyrite are often sprinkled on the orthoclase.

Polybasite [(Ag, Cu).sub.16][Sb.sub.2][S.sub.11]

Stopes 44-11-8 and 43-11-8 have produced some lustrous, black, hexagonal plates of polybasite. It is usually associated with stephanite, pyrargyrite, gypsum and aragonite and occasionally with pyrrhotite. This assemblage is always found on a limonitic crust with a border around it that is reminiscent of molten plastic. It is an interesting alteration feature that needs to be studied further.

Pyrargyrite [Ag.sub.3]Sb[S.sub.3]

Probably the most common sulfosalt, pyrargyrite occurs as deep red, hexagonal prisms up to 1 cm throughout the mine. Most crystals range from 0.5 to 2 mm in length. It occurs on shear surfaces within the massive galena where the crystals appear to be "frozen" in the fine-grained galena matrix. Pyrargyrite also occurs in the quartz-lined cavities with other sulfosalts and sulfides. The pyrargyrite crystals tarnish after long exposure to light.

Pyrite Fe[S.sub.2]

Pyrite occurs throughout the mine in a variety of habits. Vugs in the calcite vein in the intrusions along the 4270 drift contain crusts of irridescent cubes and elongated cubes on calcite crystals. Within the calcite veins of an altered porphyry are filiform pyrite crystals.

Large, lustrous groups of cubes, up to 1.5 cm on an edge, occur in fractures in the graphitic shearing zone of the 45-13-7 Stope. These occur associated with floater pyrrhotite rosettes in black, spongy wad.

Other locations in the mine produce cubes and octahedrons, or combinations of both, in chlorite-coated vugs, on quartz or on orthoclase.

Pyrostilpnite [Ag.sub.3]Sb[S.sub.3]

Pyrostilpnite is not common but occurs in small quantities in several stopes of the Silvana mine. It occurs as superb, thin, bladed orange-red crystals in fractures along with chlorite or pyrargyrite, cubanite, pyrrhotite, galena and quartz in silica-rich zones. More often than not, pyrostilpnite is intimately associated with pyrargyrite. The crystals are quite small; the largest seen are about 1 mm. Some specimens exhibit a thin, long and curved threadlike habit.

Quartz Si[O.sub.2]

Beautifully gemmy quartz crystals line the fracture cavities, making a dazzling background for the more desirable mineral species found in the same cavities. However, some unusual quartz habits that warrant attention occur in the 45-13-8 and 45-13-9 stopes. One of these is a pseudocubic quartz that is associated with another of bipyramidal habit. There are also some interestingly sceptred quartzes exhibiting a bipyramidal habit overgrowing a chlorite-coated prism. Doubly terminated quartz crystals up to 1.5 cm occur on chlorite-coated cavities in the siderite lenses.

Rutile Ti[O.sub.2]

Dark red-brown futile crystals frozen in quartzite and in calcite-filled fractures occur in rocks associated with the intrusives on the 4460 East level. This material was found during an exploratory drilling program and has not yet been found in any area actually being mined. Anatase is usually found as the titanium oxide constituent in the intrusive dikes.

Silver Ag

Native silver occurs as small platelets up to several millimeters across in massive quartz from the 4560 Stope.

Sphalerite (Zn, Fe)S

Although sphalerite is one of the main ore minerals in the mine, good crystals of it are uncommon in comparison to other crystallized sulfides and sulfosalts. However, tiny (0.5 mm), gemmy red tetrahedrons of sphalerite occur in the veinlets within the intrusive dikes. Larger (up to 1 mm) brown crystals occur in the 44-13-0 Stope. The latter are intimately associated with chalcopyrite. Both the chalcopyrite and the sphalerite exhibit a stepped habit on the octahedral faces.

Stephanite [Ag.sub.5]Sb[S.sub.4]

Stephanite occurs as lustrous hexagonal prisms and groups associated with quartz, pyrrhotite, cubanite and polybasite. Some crystals reach a length of 2 mm.

Stilbite Na[Ca.sub.2][Al.sub.5][Si.sub.13][O.sub.36][center dot]16[H.sub.2]O

Clear to white crystals of stilbite occur on heulandite in a shear zone within the intrusive rocks in the 4000 level, #4 West lateral drift. The crystals measure up to 1.5 mm in length.

Titanite CaTiSi[O.sub.5]

Titanite occurs as honey-colored crystals frozen in a hypabyssal porphyrytic quartz diorite intrusive in the 4555 East Drift. Titanite crystallized out of the original intruding melt. The rutile and anatase are found in veinlets thought to be related to subsequent deformation activity. These minerals could be the result of titanium remobilized from titanite during these events.

COLLECTING

Collecting at the Silvana mine is for the time virtually impossible. The mine is shut and most of the collectable stopes have been slashed, making the ground unsafe. A substantial amount of material was collected by Bob Attridge over the past 15 years and much of this material still needs to be unwrapped and checked for worthwhile specimens.

ACKNOWLEDGMENTS

We thank Treminco Mines for permission to collect in the mine and for the use of geological data gathered by the company. Many thanks go to Joe Nagel and Jim Mortenson for their valuable input and to Lloyd Twaites for providing specimens not represented in the authors' collections for analysis.

REFERENCES

BEAUDOIN, G., and SANGSTER, D. F. (1990) Preliminary report on the Silvana mine and other Ag-Pb-Zn deposits, northern Kokanee Range, British Columbia. British Columbia Geological Survey Branch, Geological Fieldwork 1989, Paper 1990-1, 251-255.

BRAME, S. (1979) Mineralization near the Northeast Margin of the Nelson Batholith, British Columbia. Unpublished MSc Thesis, University of Alberta, Edmonton, Alberta.

CAIRNES, C. E. (1934) Slocan Mining Camp, British Columbia. Geological Survey of Canada, Memoir 173, 137 p.

COX, J. (1979) The Geology of the Northwest Margin of the Nelson Batholith, British Columbia. Unpublished MSc Thesis, University of Alberta, Edmonton, Alberta.

CROWE, G. (1984) Slocan silver district, Southeastern British Columbia. Unpublished paper, University of British Columbia, Vancouver, British Columbia, 13 p.

DUBORD, M. P. (undated) Ore deformation textures in Pb-Zn-Ag Ores, New Denver, British Columbia. An unpublished paper, 32 p.

GWILLIM, J. C. (1896) Gold and silver ores of the Slocan, British Columbia, Canadian Record of Science, 6, 494-498.

HEDLEY, M. S. (1952) Geology and ore deposits of the Sandon area, Slocan mining camp, British Columbia. British Columbia Ministry of Energy, Mines and Petroleum Resources, Bulletin 29, 130 p.

MAY, D. (1986) Sandon: The Mining Centre of the Silvery Slocan. Robert's Roost Printing, 216 p.

PHILLIPS, S. L. (1984) More Ore in '84! - from Slogan to Success Dickenson Mines, Ltd., Unpublished report, 11 p.

PRICE, R. A., MONGER, J. W. H., and RODDICK, J. A. (1981) Cordilleran Cross-Section; Calgary to Vancouver, Trip 3, in Geological Association Field Guides to Geology and Mineral Deposits, Annual Meeting - Calgary '81, edited by Thompson, R. I. and Cook, D. G. p. 3-1 to 3-85.

REINSBAKKEN, A. (1968) Fluid Inclusion Studies of Gangue Minerals from the Slocan Mining District, British Columbia. BSc Honours Thesis, University of British Columbia, 1968.
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Author:Mauthner, Mark H.F.; Groat, Lee A.; Raudsepp, Mati; Attridge, Robert
Publication:The Mineralogical Record
Date:Nov 1, 1996
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