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The Lac Nicolet antimony mine, South Ham, Quebec.

INTRODUCTION

The locality described herein has been variously referred to as "Ham Sud," "South Ham," "Quebec Antimony mine" or "Lac Nicolet" antimony mine by different people at different times. The first of these is simply the French equivalent of the second, and refers to the township within which the locality is situated. The Quebec Antimony mine derives its name from a small exploration company that evaluated the property in the early 1970's. Interestingly, the last of these names, which has less historical validity, but is derived from the mine's proximity to Lac Nicolet (and possibly also from the Lac Nicolet Asbestos Mines company which conducted exploration work there), has become the one in common use today.

Further confusion exists with respect to its precise location within South Ham township. Older references locate the mine in Range 1, lot 28, whereas more recent authors cite lot 56 as containing the mine. Both are correct, depending upon which map is used. The pre-1900 cadastral subdivisions in the township were apparently twice as large as the ones in present usage. In spite of a number of names and locality descriptors, there is only one principal occurrence, which is situated on the south side of a hill, approximately 500 meters south-southeast of the village of St-Martyrs-Canadiens, South Ham Township, Wolfe County, Quebec, Canada. Its precise location is at 45 [degrees] 51[minutes]09[seconds] N. latitude, 71 [degrees] 32[minutes]00[seconds]W. longitude (Warwick topographic sheet 21 E/ 13, Dept. Energy Mines & Resources, Canada, 1971).

HISTORY

Discovered in 1863, the mine was first operated by Willis Russell, of Quebec City (Willimot, 1883; Obalski, 1890). Mr. Russell worked the deposit from two shafts which were sunk directly on the vein and, by 1880, 79 tons of ore had been recovered. For the next five years the mine was operated by A. H. Elliott, who built a steam-powered stamp mill on the site to concentrate the ore. A contemporary account of the operation was given by Willimot (1883), who visited there in August 1882:

Some preliminary work was being done by a small gang of men, who were employed removing detached pieces of rock from the bottom of the shaft, which had caved in through unskillful working, having caused the timbers to give way. It is the intention of the owner to sink 10 fathoms deeper. 15 yards off, a double shaft has been sunk to a depth of 100 feet. . . . Two or three levels have been driven short distances, but with what result I was unable to ascertain; judging from what had been excavated, none of the ore would average more than 5 percent, exclusive of some very rich pockets said to have been extracted. . . . The bedded material averages 5 percent, and has to be concentrated to 8 percent before it is marketable. This is accomplished by first passing the ore through a set of stamps; a stream of water then carries the crushed material on to a rubber belt about four feet wide, revolving at a slight inclination, by which the heavier particles are carried under, to the receiving trough, whilst the lighter portions pass off with the water. I have no doubt that a great deal of the oxide must be lost, and also portions of the native metal. On examining some of the slime numerous shining particles of antimony could be seen. A large commodious building has been erected, wherein is stationed an 18-horse power engine.

In 1886, the property was taken over by Dr. J. Reed, who drove a 94-meter drainage adit through the hillside to intersect the bottom of the 30-meter shaft. By the following year, a quantity of ore had been shipped to Portland and smelted at the Bartlett Smelting Works, with favorable results. However, the lack of a market, inefficient concentration, uncertain ore reserves and competition from antimony deposits in Nova Scotia and New Brunswick soon took their toll, effectively shutting down operations by 1889. Obalski (1890) described the occurrence:

The different [antimony] species are noticeable in bluish quartz veins cropping out at the surface. The main vein . . . sometimes showing a thickness of two feet . . . has been traced for a distance of half a mile, and portions are visibly mineralized even on the surface in thicknesses of 3 to 4 inches. The thickness and richness of the vein varies as you descend, the quartz sometimes being permeated with the acicular crystals of the sulfides and the mineral at others being bunched or concentrated in rich pockets, some of which, struck in shafts 1 and 2 of the old workings, showed - it is said - as much as 2-1/2 feet in thickness.

The recent works appear to us to have established the fact that, at a depth of 100 feet, the quartz vein has a thickness of 6 feet. . . . The workings consist of two shafts of 60 and 100 feet respectively, located at a distance of 40 feet from each other and connected at the bottom by a drift, which has been prolonged for 70 feet along the vein. . . . It is said that from the old workings, 180 tons of the mineral were extracted and shipped. Since then no regular work has been done, apart from driving the adit just referred to, and only a few men have been employed to keep the mine in order.

Except for perhaps an occasional visit by mineral collectors, the mine appears to have lain idle for the next half century. In 1940, Reed Realties, Ltd. of Montreal, cleared the adit and did some exploratory work in the underground workings, but did not develop the mine. A decade later in 1951, Lac Nicolet Asbestos Mines, Ltd. conducted a small scale diamond drilling program, as did Sullico Mines, Ltd. in 1964, and Quebec Antimony Mines, Ltd., who estimated a 75,000-ton ore reserve at 2.5% Sb in 1970-1972. Mr. Maxwell Juby of Montreal staked the property in 1985-1986 to sample for precious metals, but nothing of economic interest was found. In the summer of 1986, the Canadian Museum of Nature mapped the occurrence and collected specimens. Additional specimens were collected by both the museum and by Grenville Minerals the following summer, and numerous collectors have visited the locality since then. The most recent studies of the deposit were by Wight (1985), Gauthier et al. (1989), Robinson (1991), Normand et al. (1991, 1994) and Normand (1993).

Today, virtually all the old dumps, the adit and buildings have been obliterated by the development of gravel pits near the mine site. It is still possible to collect from the surface exposure of the vein a few meters east of the shafts and, although large, high-quality cabinet specimens are rarely found, fairly good smaller specimens and excellent micro-mounts of most of the minerals described here can still be obtained. The mining rights to the property are presently under claim by Mr. Bertrand Brassard of Coleraine, Quebec, while the local municipality of St-Martyrs-Canadiens controls surface access. With prior permission, casual surface collecting by hobbyists is permitted, but commercial collecting and collecting from the underground workings is forbidden. In addition, the gravel pits that surround the principal occurrence are frequently used for target shooting, further necessitating the need for advance visitation arrangements.

GEOLOGY

The Lac Nicolet antimony mine is located in the Caldwell Group of metasedimentary and igneous rocks that form a portion of the Appalachian geological province. These rocks are upper Cambrian to lower Ordovician in age and have been regionally metamorphosed to greenschist facies (Riordon, 1954; St-Julien, 1972; Harron, 1976). The metasedimentary rocks consist chiefly of slates, phyllites and quartzites, and the igneous rocks have been heavily serpentinized. It is believed that in mid-to-late Ordovician time the Ascot-Weedon island arcs and late Precambrian-Cambrian Chain Lakes massif collided obliquely with the North American continent (Doolan et al., 1982; Gauthier et al., 1989). Major offset and reverse faulting probably caused secondary shearing and tension fractures to develop in adjacent competent rocks, which in turn acted as channels for hydrothermal quartz-metal vein emplacement in Acadian time.

The antimony mineralization observed at Lac Nicolet probably originated in such a manner. The mine itself is situated in a siliceous phyllitic unit, very near a major fault contact with serpentinized peridotite [ILLUSTRATION FOR FIGURE 3 OMITTED]. In the underground workings most of the vein has either been removed by mining or is presently inaccessible due to caving and seasonal flooding. What little is left is poorly exposed, and shows a pinch-and-swell pattern. The rock in proximity to the vein is noticeably sheared and silicified. Even the vein itself is locally sheared and brecciated, indicating movement during and after its eraplacement. Stages of mineralization and faulting were probably pulsating, as evidenced by mylonitized fragments of early dark-colored quartz in later sheared native antimony, drag-folding in the schistosity of the rocks at their contact with the main vein, and the presence of slickensides on vein-parallel fault planes.

Older descriptions (Willimot, 1883; Obalski, 1890; Dresser, 1914; etc.) state that the vein is traceable for about a kilometer on strike, and mention additional workings east of the main shafts. The authors were able to locate two small prospect pits with minor antimony mineralization: one approximately 100 meters northeast of the main workings and another approximately 300 meters to the east. Diamond-drilling logs from both the Sullico and Quebec Antimony projects were unable to prove a continuous extension of the vein, and the best estimate of reserves is probably that of Quebec Antimony Mines, Ltd., at 68,025 tons at 2.5% Sb (or 181,400 tons at 1.7% Sb).

MINERALOGY

Antimony mineralization at the Lac Nicolet mine may be divided into three general types, based on their occurrence and dominant mineral assemblages: (1) isolated grains in the country rock, (2) a gudmundite-albite-dolomite assemblage, and (3) quartz-stibnite-antimony veins. The predominance of stibnite or native antimony in the latter veins was probably controlled by local activities of sulfur, oxygen and hydrogen during vein formation. A number of secondary species, such as aragonite and gypsum, have also been identified from the deposit. These probably formed by weathering, and are unrelated to the antimony mineralization. Table 1 summarizes the occurrence of these minerals. Unless otherwise noted, the identity of all the species has been verified by X-ray and/or microprobe analysis.

Albite NaAl[Si.sub.3][O.sub.8]

Albite is an abundant accessory mineral in the gudmundite-albite-dolomite assemblage. In cavities it forms glassy, colorless, milky to transparent, tabular crystals up to 7 mm, twinned on the albite law. It is nearly always associated with abundant quartz, gudmundite and dolomite, often with stibnite, and occasionally with pyrrhotite or berthierite.

Antimony Sb

One of the primary ore minerals, native antimony occurs most commonly as pure, massive vein sections up to 15 cm wide. Most vein sections vary in color from bright, tin-white to dull gray, and show a somewhat granular to cataclastic texture on freshly broken surfaces. Abundant shards of quartz are apparent when viewed under the microscope. Occasionally, some of the massive antimony contains small cavities lined with brilliant, silvery, microscopic crystals, but these are rare. SEM examination of such specimens reveals the crystals to be aggregates of intergrown rhombohedra. Antimony also occurs sparingly in cavities in the gudmundite-albite-dolomite assemblage as microscopic, occasionally iridescent, granular to spongy masses.

Aragonite CaC[O.sub.3]

Aragonite has been identified on a single specimen of limonite collected from a surface exposure of the main vein, directly below and east of the two mine shafts. The crystals occur as white to colorless prismatic individuals and radial aggregates up to 1 mm, and are likely the product of near-surface weathering.

Berthierite Fe[Sb.sub.2][S.sub.4]

Berthierite occurs both as rich black masses and more sparingly as iridescent, prismatic, microcrystals in the gudmundite-albite-dolomite assemblage. It has also been identified as granular black masses associated with stibnite, schafarzikite and metastibnite, and rarely as prismatic crystals to 2 cm in the quartz-stibnite-antimony veins. In both associations, berthierite is virtually indistinguishable from stibnite without employing optical, X-ray or microprobe techniques. Berthierite is not as common as stibnite, and many specimens labeled as berthierite, when X-rayed, have proven to be stibnite.

Calcite CaC[O.sub.3]

Calcite has been collected from a single occurrence in the upper level of the underground workings near the westernmost shaft, where it forms gray-white cleavage masses up to 3 cm in a breccia vein. The calcite fluoresces a moderate purplish red in both longwave and shortwave ultraviolet light. No other species is associated.

Chlorite group [(Mg,[Fe.sup.2+]).sub.5]Al([Si.sub.3]Al)[O.sub.10][(OH).sub.8]

Aggregates of microscopic, micaceous, velvety, green-brown spheres are occasionally observed in cavities in both the quartz-stibnite-antimony veins and the gudmundite-albite-dolomite assemblage. X-ray patterns obtained from these spheroidal aggregates show them to be members of the chlorite group, and their EDS spectra indicate they are predominantly Mg-Fe aluminosilicates, suggesting they are most likely intermediate in composition between clinochlore and chamosite.

Dolomite CaMg[(C[O.sub.3]).sub.2]

Dolomite appears to occur exclusively in the gudmundite-albite-dolomite assemblage. It commonly forms sharp rhombohedral crystals up to 2 mm, associated with quartz, albite, stibnite and gudmundite. Semiquantitative EDS microprobe analysis shows this dolomite to be enriched in iron, and is thus a ferroan dolomite. While most crystals are translucent to opaque and pale yellow-brown in color, some may appear nearly colorless and pseudo-octahedral in habit, due to nearly equal development of rhomb and pinacoid faces. Such crystals have often been mistaken for senarmontite. However, the two minerals are easily differentiated, since the senarmontite is typically more lustrous, gray to colorless, isotropic, lacks rhombohedral cleavage, has a higher specific gravity, and is virtually absent from the gudmundite-albite-dolomite assemblage.

Galena PbS

Galena is very rare at the Lac Nicolet deposit, and has been identified on only a very few specimens collected from the dumps. It has been observed as tiny, 1-mm cleavages associated with resinous, pale brown sphalerite and minor gudmundite in quartz, as microscopic inclusions in gudmundite, and as a granular gray mass replacing stibnite on one specimen.

Goethite [Fe.sup.3+]O(OH)

Goethite occurs abundantly as rusty brown coatings on many of the rocks and joint surfaces in the general vicinity of the mine, as the result of chemical weathering of iron-bearing minerals. It has also been observed replacing tabular hexagonal prisms of pyrrhotite in the gudmundite-albite-dolomite assemblage.

Gudmundite FeSbS

Worldwide, gudmundite is a relatively uncommon mineral, but it occurs fairly abundantly at the Lac Nicolet mine as 1-2 mm prismatic crystals generally resembling marcasite. An examination of heavy mineral separates indicates that gudmundite (at 85 volume %) is the most abundant ore mineral in the deposit (Mathieu and Bruce, 1973). Well-formed crystals of gudmundite occur almost exclusively in the gudmundite-albite-dolomite assemblage, and are frequently associated with minor stibnite and quartz. Occasionally, small isolated crystals can be observed in the host rock in the general vicinity of the mine and the small prospect 100 meters to the northeast, but the best specimens have been collected from what remains of the early-mined dump material. Most of the gudmundite has a tarnished brassy brown color, but is bright tin-white on freshly broken surfaces. Electron microprobe analyses indicate the gudmundite is essentially pure FeSbS.

Gypsum CaS[O.sub.4][multiplied by]2[H.sub.2]O

Colorless crystals of gypsum up to 2 mm were collected from the dumps by Hamilton Stitt, circa 1968. The crystals form transparent stellate groups several millimeters across on goethite-coated phyllite, and may be of post-mining origin. The only two specimens known to us are preserved in the collections of Quintin Wight and Peter Tarassoff.

Halloysite [Al.sub.2][Si.sub.2][O.sub.5][(OH).sub.4]

Halloysite occurs as microscopic cream-white balls and desiccated masses lining fractures and cavities in some of the quartz-stibnite-antimony veins. It is not common.

Kermesite [Sb.sub.2][S.sub.2]O

Of all the minerals found at the Lac Nicolet mine, the most famous and visually attractive is probably kermesite. This mineral occurs in a variety of habits and colors ranging from powdery red coatings on fracture surfaces to purplish red acicular crystals to 5 cm, crimson-red tufts of microcrystals and purplish red velvety crystal masses several centimeters across. Micromounts of kermesite associated with stibnite, valentinite and quartz exist in abundance, and are perhaps the best known specimens from this locality. Unfortunately, large, high-quality specimens have been preserved in relatively few collections. To our knowledge, the best are probably those in the Canadian Museum of Nature (Ottawa) and the Lucius Hubbard collection at the A. E. Seaman Mineralogical Museum in Houghton, Michigan. The fact that similar specimens were probably lost to the mill and smelter due to general disinterest is indeed a tragedy, for those that have been preserved rank with the world's best for the species.

While kermesite is relatively abundant in the quartz-stibnite-antimony veins, it is virtually absent in the gudmundite-albite-dolomite assemblage. In some specimens kermesite replaces stibnite, and may itself be replaced by stibiconite. Other specimens, however, show no evidence of stibnite replacement. Kermesite formation may be regulated by local changes in the chemical activities of various sulfur species, oxygen and hydrogen, and possibly other factors such as temperature (Krupp, 1988).

Malachite [Chemical Equation Omitted]

Malachite has been identified on a single specimen collected from the surface exposure of the main vein directly above the underground workings, where it forms a powdery green stain on and in stibiconite.

Metastibnite [Sb.sub.2][S.sub.3]

Metastibnite occurs abundantly as a red powder, coating other minerals and joint surfaces in the immediate vicinity of the quartz-stibnite-antimony veins. As far as we can determine, this is the first reported occurrence of metastibnite in Canada. While metastibnite is rather common at the Lac Nicolet mine, its identity eluded the authors for quite some time. Metastibnite typically appears more red than kermesite, but it is difficult to distinguish from that mineral unless a simultaneous comparison is made. Thus, initially we assumed the mineral was just fine-grained kermesite. However, X-ray powder patterns showed senarmontite ([Sb.sub.2][O.sub.3]) as the only mineral present! Confusing the issue further, subsequent microprobe investigation of the same samples showed them to be [Sb.sub.2][S.sub.3], or stibnite. Since neither senarmontite nor stibnite is known as a red powdery mineral, more samples were analyzed, which only confirmed the previous results. Finally, a rather large, 2-cm piece of the material was prepared for SEM examination, which revealed the presence of two phases: submicroscopic octahedrons of senarmontite along with a globular, somewhat botryoidal phase with Sb:S = 2:3. Since metastibnite is amorphous, its presence could not be detected by X-ray analysis, nor could the presence of oxygen in the senarmontite be detected by the EDS microprobe technique in use.

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

A single 5-mm crystal of white microcline was found in a specimen collected from a rubble pile in the lower underground workings of the mine. Abundant quartz, stibnite, kermesite and stibiconite as associated species suggests it is from one of the quartz-stibnite-antimony veins.

Montmorillonite [(Na,Ca).sub.0,3][(Al,Mg).sub.2][Si.sub.4][O.sub.10][(OH).sub.2][ multiplied by]n[H.sub.2]O

Several specimens of microscopic, tan-to-beige spheroids extracted from various cavities in quartz-stibnite-antimony veins gave X-ray patterns similar to that of montmorillonite. Qualitative EDS microprobe analysis showed these samples to be essentially aluminum silicate, often mixed with minor amounts of iron and antimony minerals.

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

Microscopic white crystals of orthoclase have been noted on two specimens. The first of these was collected from a sheared quartz vein adjacent to a native antimony vein in the upper level of the underground workings, and the second came from dump material. The crystals on both specimens show the typical "adularia" habit, and average 0.5-2.0 mm in maximum dimension. Associated species are quartz and minor kermesite, stibnite and chlorite.

Pyrrhotite [Fe.sub.1-x]S

Pyrrhotite is regularly observed as a minor accessory mineral in the gudmundite-albite-dolomite assemblage, where it forms tabular, hexagonal plates up to 2 mm across, frequently replaced by goethite. Pyrrhotite also occurs as an abundant but minor accessory mineral in the metasedimentary rocks near the principal vein.

Quartz Si[O.sub.2]

While quartz is one of the most common species at Lac Nicolet, and may be observed on almost any specimen, it seldom occurs in collector-quality crystals. Undoubtedly the most aesthetic specimens are the tiny, Herkimer diamond-like crystals that occur in both the gudmundite-albite-dolomite assemblage and the quartz-stibnite-antimony veins, associated with kermesite, stibnite and valentinite as micromount specimens. Larger crystals are typically etched and cloudy, and seldom exceed a centimeter across. One notable exception, however, is a doubly terminated, 2.5-cm crystal with stibnite (?) inclusions in the collection of Charles Normand.

Schafarzikite [Chemical Equation Omitted]

In the course of identifying the myriad red powdery minerals observed on fracture surfaces at Lac Nicolet, the rare mineral schafarzikite was identified by X-ray diffraction, and confirmed by semiquantitative EDS microprobe analysis. So far it has been identified on only a few specimens, and is virtually indistinguishable in hand specimens from the metastibnite and powdery kermesite with which it is associated. Berthierite is also present on the specimen, and the schafarzikite may have been formed by alteration of that mineral. Like metastibnite, we believe this to be the first reported occurrence of schafarzikite in Canada.

Senarmontite [Sb.sub.2][O.sub.3]

Senarmontite occurs rather abundantly in some of the cavities in the quartz-stibnite-antimony veins, where it forms colorless-to-gray transparent octahedrons that average a millimeter across. Crystals larger than 1-2 millimeters are very rare, though a unique 8-millimeter single crystal resembling those from Hamimat, Constantine, Algeria, is preserved in the Hubbard collection at the A. E. Seaman Museum.

Sphalerite ZnS

Like galena, sphalerite is very rare at the Lac Nicolet deposit, having been confirmed in only a very few specimens as tiny brown grains and cleavages up to 3-4 mm in quartz associated with either galena or gudmundite.

Stibiconite [Chemical Equation Omitted]

Stibiconite is an abundant alteration product at Lac Nicolet, particularly in the quartz-stibnite-antimony veins. It appears late in the paragenesis of these veins, and forms powdery coatings on virtually all earlier-formed antimony minerals. The coatings may be pure white, ivory, beige, yellow, or orange-brown in color, and vary in thickness from 3 cm to a faint dusting that is barely perceivable. Stibiconite frequently replaces both stibnite and kermesite, forming pseudomorphs after these minerals.

Stibnite [Sb.sub.2][S.sub.3]

Along with gudmundite and native antimony, stibnite was one of the primary ore minerals mined from this deposit. It occurs as densely packed, interlocking, millimeter-sized cleavages in veins, as silvery-gray, metallic, terminated crystals 1-2 cm long in cavities (first generation crystals), as radiating (occasionally iridescent) black tufts of microcrystals (second generation crystals), and as thin, silvery sheets resembling aluminum foil coating fractures in the host rock adjacent to some of the quartz-stibnite-antimony veins. Radiating, silvery black microcrystals are common in some cavities in the gudmundite-albite-dolomite assemblage. It is reported that a crystal 15 cm long was found by a worker with the Quebec Antimony Mine diamond drilling project in the early 1970's, but the whereabouts of the specimen both then and now is unknown (Quintin Wight, personal communication).

Stibnite has also been observed replacing pyrrhotite crystals in both hand specimens and polished sections. The former are relatively uncommon, and generally resemble graphite. X-ray and microprobe analyses of these pseudomorphs confirm the original hexagonal mineral as pyrrhotite.

Tetrahedrite [(Cu,Fe).sub.12][Sb.sub.4][S.sub.13]

Lustrous, black, tristetrahedral crystals of tetrahedrite, some of them modified by deltohedron faces, were found on a single specimen collected from rubble in the upper level of the underground workings. The crystals are generally less than 0.5 mm across, and are associated with stibnite, quartz and granular brown microcrystals of senarmontite in cavities in quartz. The assemblage is otherwise typical of the quartz-stibnite-antimony vein mineralization. Tetrahedrite also has been identified as sparse, black masses to 2 mm in dense, gray quartz in a second specimen collected from the underground workings, and silver-bearing tetrahedrite occurs as a trace constitute in the altered metasedimentary rocks with pyrrhotite, chalcopyrite and ullmannite.

Valentinite [Sb.sub.2][O.sub.3]

Crystals of valentinite occur in at least six different habits, and are frequently encountered in the quartz-stibnite-antimony veins. The most commonly associated species are quartz, stibnite, native antimony, kermesite and senarmontite. The valentinite is always well-crystallized, and is most commonly white or grayish white, though some of the larger crystals may appear beige to caramel-yellow, or rarely even red due to associated metastibnite. The largest crystals approach a centimeter in length, but these are rare. Usually, they are much smaller, averaging 1 to 3 mm; but from a crystallographic standpoint, they are perhaps the most interesting of all the minerals to be found at the locality.

There are at least six different habits of valentinite at the Lac Nicolet mine. Miller indices for the various forms were obtained by optical goniometry from crystals whose orientation was first established by X-ray precession photographs. The first three habits are encountered with about equal frequency, whereas the latter three are relatively uncommon. Variations of these and additional habits have been observed, but only rarely, and usually only with the aid of SEM magnification. Under a regular binocular microscope, most such specimens appear as crusts of microscopic, acicular, white crystals. Because they are of minimal significance, they will not be described.

Crystals of habit 1 resemble pseudotetragonal dipyramids, especially when observed growing from the matrix along [010]. This is due to nearly equal development of forms {011} and {110} and, if viewed under the microscope, the true orthorhombic symmetry of these crystals is readily apparent. The {110} faces are typically smooth and lustrous, and, of course, parallel to the {110} cleavage planes. Small {100}, {010} and {001} pinacoids may also be present. The {011} faces are duller and typically rounded, which makes their identification by optical goniometry somewhat tenuous. Reflections corresponding to the following forms have been observed as oscillatory growths on these faces: {012}, {013}, {014}?, {0.16.1}?, {102}?, {103}, {104}? and {506}. Crystals of habit 2 have the same forms as those of habit 1, but are either elongate or stacked in parallel growth along [001], resulting in bluntly terminated prisms and wheat sheaf-like growths.

The third habit is characterized by large {010} pinacoids bounded by {110} and {032} prisms. Crystals of this habit are nearly always elongate on [100], and often slightly divergent along [001]. Crystals of habit 4 are also elongated on [100], but have large, tabular {001} pinacoids. Other forms on these crystals include {100} and {010} pinacoids, and prisms {110}, {1.0.10}?, {021} and {081}?

Crystals of the last two habits are perhaps the most interesting of all, and certainly the least common, having been observed on only about a half dozen specimens. Both form spiky oriented overgrowths projecting in parallel position from the {110} faces of crystals of habit 2. Both are elongate on [100], but differ with respect to the forms present. Habit 5 crystals have relatively large {010} and {001} pinacoids, with smaller {110}, {011} and {100} faces, and show oscillatory growth between {001} and unidentified {hk0} or {hk1} faces, giving a false impression of twinning. A small {h01} prism also is occasionally present. Habit 6 is similar, except the {001} and {011} forms are replaced by steep {h01} prisms that yield reflections approximating {1.0.12} and give a distinct sawtooth appearance when viewed along [010] in parallel growths. The sharp boundaries between these overgrowths and their template crystals suggest they probably formed as a second generation of valentinite rather than by dissolution.

Other Species

During the course of this study, several other minerals were noted while examining polished sections by electron microprobe. A number of these were found in only a single section and all occur as singular microscopic grains or inclusions in other minerals. None is of collector quality, and none exists in sufficient size or quantity to permit X-ray analysis. Among these minerals are arsenopyrite and chalcostibite, both of which occur sparingly as isolated euhedral crystals in some of the massive native antimony; jamesonite, which was noted as an inclusion in a single grain of gudmundite; and rare, scattered grains of pyrite and chalcopyrite. Microscopic grains of zircon, rutile, ilmenite, xenotime-(Y) and monazite-(Ce) are frequently observed in some of the metasedimentary rocks near the main showing, along with less frequent grains of argentiferous tetrahedrite, ullmannite, sphalerite and chalcopyrite in altered zones. Disseminated grains of chromite and pentlandite are present in the serpentinized peridotite approximately 50 meters to the north. Rarely glaucodot (?), and breithauptite occur as inclusions in some of the pentlandite grains. Backscattered electron images of some of the pentlandite and associated minerals show chemical alteration along fractures and grain boundaries. Electron microprobe analyses of these alteration products typically give variable amounts of Ni, Fe, Co, Mg, Ca, Si, As, Sb and S, and variable analytic sums, suggesting they are probably mixtures. Clinozoisite, epidote, prehnite and jarosite also have been reported from the occurrence (Gauthier et al., 1989; Sabina, 1967), but have not been observed by the authors.

PARAGENESIS

Microscopic examination of numerous polished sections and over 1000 hand specimens has established the paragenetic trends diagrammed in Figure 20. In the gudmundite-albite-dolomite assemblage, quartz, albite, pyrrhotite and dolomite appear to be the earliest minerals to have formed, followed by berthierite, gudmundite, stibnite and adularia (?), then by minor native antimony and chlorite. In the quartz-stibnite-antimony veins, quartz was the first mineral to crystallize, followed in succession by berthierite, stibnite, native antimony, a second generation of stibnite, kermesite, valentinite (+ minor senarmontite), chlorite and senarmontite. Locally, a second generation of valentinite and kermesite as well as a third generation of stibnite appear to have crystallized under equilibrium conditions with the main generation of senarmontite. Metastibnite, schafarzikite, stibiconite and very minor senarmontite appear late in the paragenetic sequence, and may be either very late hypogene or supergene minerals.

Preliminary microthermometric measurements of fluid inclusions in quartz suggest crystallization temperatures between 200-250 [degrees] C. This temperature range is consistent with the maximum thermal stability limit for gudmundite of -280 [degrees] C (Clark, 1966) and the berthierite-pyrrhotite assemblage which is stable about 160 [degrees] C (Seal et al., 1992). Microcryometric and gas-chromatographic data indicate the presence of [CH.sub.4]-[N.sub.2]-rich and C[O.sub.2]-poor fluids with low salinity (Normand et al., in preparation). Homogenization behavior of monophase [CH.sub.4]-rich inclusions suggests that pressures at least above 400-500 bars prevailed.

The paragenetic trends described above for the vug minerals suggest a history of increasing oxygen fugacity, decreasing temperature and locally variable, but generally decreasing sulfur fugacity. The reducing conditions required for the main stage of ore mineralization may have been maintained by fluid/rock interaction and/or mixing with fluids derived from the nearby serpentinites (Normand et al., 1995?). A progressive increase in oxidizing conditions is confirmed by the sequential increase in the valence of antimony, from 0 in native antimony to 3+ in stibnite, kermesite, valentinite and senarmontite, to 5+ in the stibiconite. The presence of [(OH).sup.-] in the stibiconite further suggests either an increase in pH and/or a drop in temperature, consistent with a geological model of typical oxide zone development as erosion of overlying rock exposed the sheared and brecciated metal-bearing veins to oxygenated groundwater.
Table 1. Distribution of Species.


                 Gudmundite-     Quartz-
Country          Albite-         Stibnite
Rock or          Dolomite        Antimony           Weathering
Isolated         Assemblage      Veins              Products


Albite           Albite          Antimony           Aragonite
Breithauptite    Antimony        Arsenopyrite       Goethite
Calcite          Berthierite     Berthierite        Gypsum
Chalcopyrite     Chlorite        Chalcostibite      Malachite
Chlorite         Dolomite        Chlorite           Metastibnite?
Chromite         Galena          Galena             Schafarzikite?
Dolomite         Gudmundite      Halloysite         Senarmontite?
Galena           Jamesonite      Kermesite          Stibiconite?
Glaucodot (?)    Orthoclase      Metastibnite
Gudmundite       Pyrrhotite      Microcline
Ilmenite         Quartz          Montmorillonite
Pyrite           Stibnite        Orthoclase
Microcline                       Quartz
Monazite-(Ce)                    Schafarzikite
Pentlandite                      Senarmontite
Pyrrhotite                       Sphalerite
Quartz                           Stibiconite
Rutile                           Stibnite
Serpentine                       Tetrahedrite
Sphalerite                       Valentinite
Tetrahedrite
Ullmanite
Xenotime-(Y)
Zircon


ACKNOWLEDGMENTS

Thanks must be given to Maxwell Juby, Bertrand Brassard and Jeanine Evers, who facilitated our visits to the mine, to Stanley Dyl for providing information on the Hubbard collection, to Simon Morneau for lending his stibnite specimen for photography, to Michel Picard, Reinhard Wegner, Brad Wilson and Darryl MacFarlane for their assistance in the field, to Peter Tarassoff for his help researching the history of the deposit, to Quintin Wight for his photomicrographs and assistance with the crystal drawings, and to Jerry Van Velthuizen who provided the X-ray diffraction analyses. Funding for this project was in part made possible through a Canadian Museum of Nature RAC grant (ENPE 100) to GWR.

REFERENCES

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GRICE, J. D., and WILLIAMS, R. (1979) Famous mineral localities: The Jeffrey mine, Asbestos, Quebec. Mineralogical Record, 10, 69-80.

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NORMAND, C., GAUTHIER, M., and JEBRAK, M. (1991) Antimony mineralization in the Brompton-Baie Verte Structural zone, Quebec (Abstract). Joint Annual Meeting of the Geological Association of Canada, Mineralogical Association of Canada and Society of Economic Geologists, Program with Abstracts, Toronto (1991), p. A91.

NORMAND, C., GAUTHIER, M., and JEBRAK, M. (1995?) The Quebec Antimony deposit: an example of gudmundite-native antimony mineralization in the Ophiolitic Melange of the southeastern Quebec Appalachians. (paper submitted to Economic Geology, April, 1994).

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Title Annotation:Famous Mineral Localities
Author:Robinson, George W.; Normand, Charles
Publication:The Mineralogical Record
Date:Mar 1, 1996
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