Introduction
On the outskirts of Halifax begin the granite rocks that extend over most of southern Nova Scotia. In the area around Bayers Lake and Timberlea are numerous small veins, pockets and lenses. In some cases the crystallization becomes coarse, forming a pegmatite. An early, and now defunct, exposure was a roadcut at the intersection of the St. Margarets Bay Road and Highway 103, within sight of the Bayers Lake Industrial Park. This was excavated and collected in 1978. The intersection cut through a good sized pegmatite for the area. Little remains today, but when the cut was first made, many specimens were found. Around 2010, expansion of the industrial park and the twinning of Highway 103 exposed new rock that has produced some very nice specimens. In 2018, another expansion of the industrial park was made. Finally, this article includes a couple additional minerals from the small Governor Lake pegmatite.
History
The history of this area is more of an ongoing description of urban development than anything else, although the story does start with a worked deposit. Near Governor Lake, a dyke was discovered in 1920 and opened up in 1921 by a Mr. Norman McMillan. He quarried about 200 tons of feldspar and shipped 16 tons to Brandram-Henderson Company for testing (Messervey 1933).
In the 1970s a new interchange was constructed near Bayer's Lake to connect to Highway 103. I'm guessing a much of the start of the highway was also built at the same time, but I'm not sure. The interchange passed through a pegmatite zone and was, for a short time, a popular collecting spot. Many years later the stretch of highway between Bayer's Lake and Timberlea was twinned, but there is no indication that it was collected at the time. The southern and western areas of the Bayer's Lake industrial part have expanded in several phases over the years. An expansion in the early 2000s produced a considerable quantity of material, including large, sometimes gemmy, smoky quartz crystals.
Geology
The granite is part of the South Mountain Batholith which covers a large portion of southwest Nova Scotia. This particular area is the Halifax Pluton (O'Reilly 2000). The Bayers Lake pegmatites are near the edge of the batholith. Less than a kilometer away one finds metamorphisized slates and shales from the Halifax Formation. The granites are Devonian-Carboniferous in age (O'Reilly 2000).
Nice examples of graphic granite were common in the 2018 expansion area. These are mixtures of quartz and feldspar, creating a pattern that looks vaguely like cuniform writing.
Mineralogy
Minerals reported from Bayers Lake and the highway include microcline, albite, muscovite, quartz, schorl, apatite, cordierite pinite, garnet, meta-autunite, and an unidentified green clay mineral. Anatase has been identified from the Governor Lake pegmatite and a single specimen from Highway 103 also contains a TiO2 phase. Several other minerals have also been identified by Don Doell from Governor Lake including metatorbernite, pyromorphite, zircon, goethite, covellite, and sekaninaite.
Many microminerals were found in an aplite dyke in the 2018 expansion area. A small zone, maybe 100x50 cm, was very crumbly and rotted. It was iron stained, suggesting some sulfides, like pyrite, had rotted out. The rock was very porous with countless small pockets filled with interesting but very tiny crystals. Species included fluorapatite, fluorite, rutile, anatase, titanite, gypsum, and natrojarosite. In the text below, I'll refer to this zone as the 2018 pod.
Table 1: Minerals reported from Bayers Lake, Governor Lake and Timberlea.
Albite - NaAlSi3O8
Albite crystals were common at the pegmatites in the 2010 Bayers Lake Industrial Park extension. Some of these reached several centimeters in size and had good luster, making them somewhat attractive. A few good specimens were also recovered from the 2018 expansion.
Almandine (Garnet) - Fe2+3Al2(SiO4)3
Small reddish garnets in thin aplite dykes are reported by Andrew Macrae (pers. comm.) from the south entrance of the Industrial Park, an area that is now built over. Other small garnets have been found in the 2018 expansion. There is no analysis, that I'm aware of, of garnets from this exact area, but there are several from other spots in the Halifax Pluton, and they are all almandine. For example, Allan and Clarke (1981) analyse samples from Kearney Lake, about 4-5 km away and the garnets are 67-78 mol% almandine.
Anatase - TiO2
Anatase has been confirmed from the Governor Lake pegmatite using Raman spectrscopy and single crystal X-ray diffraction. A photo and analysis of the specimen can be found here, on the U. Arizona RRUFF website. Rutile has also been identified from Bayer's Lake.
Doug Wilson gave me a specimen from Highway 103 with lustrous black blocky crystals on quartz and albite that was identified as one of the TiO2 polymorphs using qualitative EDS. I'm putting it here with the anatase until I have further details. Although the crystal appear to be black at first glance, there do seem to be dark brown internal reflections under magnification.
Cordierite - (Mg,Fe)2Al3(AlSi5O18) -
Sekaninaite - (Fe,Mg)2Al3(AlSi5O18)
These two species forms a continuous series, with sekaninaite being iron dominant and cordierite being magnesium dominant. Most of the 'cordierites' from this locality have altered to pinite, but a few specimens have been found that are unaltered and are actually gemmy, though highly fractured. Specimens with gemmy areas have colors of grayish-blue to brown.
Because the two species form a series and both have been found here, each specimen would have to be checked to get a proper species identification. However, collector Don Doell did have a number of specimens tested and reports that the majority were actually sekaninaite. I'm not sure if crystals can be zoned with both species present in the same crystal.
Covellite - CuS
Only found at Governor Lake pegmatite. Reported by Don Doell as iridescent black crystals.
Fluorapatite - Ca5(PO4)3F
Local collector Doug Wilson recalls apatite crystals from the Highway 103 overpass of St. Margarets Bay Road. They are described as prismatic and up to about 1 cm in size. At least one of the apatites was a very attractive blue color and gemmy. The Canadian Museum of Nature has a specimen from this find that is not gemmy but has a vibrant blue color. Tiny blue crystals were also found during the 2018 expansion.
The ~2010 diggings near the Bayers Lake extension produced a very small number of apatites. The ~2018 diggings produced more crystals, of better quality and larger size. The crystals are tabular to equant, often with bevelled edges. The color varies between crystals and includes cream-white, gray-blue, bluish-brown, pink, green, and purplish-blue. These have not been probed to determine what type of apatite they are - in the section header I'm assuming they are fluorapatite.
As mentioned above the crystals frequently show bevelled edges. Measurements of a lustrous crystal on a goniometer gave excellent matches to the simple modifying forms x{10·1} and r{10·2}. The presence and strength of each of these forms varies between crystals and even around the circumference of a given crystal. A drawing of an ideal crystal with these forms is shown below.
Some of these apatites are also fluorescent, including orange fluorescence under long-wave UV.
Fluorite - CaF2
Fluorite is rare in this area. Some very dark crystals were found in an aplite dyke in the 2018 expansion area. The smallest crystals showed a dark purple color but larger crystal fragments appeared nearly black. Black fluorite from Germany is called antozonite and also 'fetid fluorite' for a smell created when it is crushed (Schmedt auf der Günne, et al., 2012). Similar material is known from many other localities including Canada. It has been determined for that material that the black color is due to radiation. The radiation creates fluorine gas and clusters of metallic calcium. The fluorine gas is released in crushing and reacts with oxygen and water in the surrounding air to produce ozone, and thus creating the 'fetid' smell. The metallic calcium is responsible for the black color. I have not tested this local material for smell, but the color certainly matches and the expectation of radiation is very reasonable.
Gypsum - CaSO4 · 2H2O
A few tiny crystals and sprays of gypsum were found as secondary minerals in the rotten 2018 pod. The sulfate was likely derived from rotting pyrite. Identification was by Raman spectroscopy and supported by crystal shape and environment.
Meta-autunite - Ca(UO2)2(PO4)2·6-8H2O
Yellow tabular to platey crystals were found along one section of Highway 103 towards Timberlea. Although identification is visual only, meta-autunite is a widely reported mineral from the South Mountain Batholith. Some of the crystals were found loose in the gravel. Others were still attached to smoky quartz crystals. They fluoresce a bright neon green. The fluorescence is so strong, it can easily be seen at regular room light-levels.
Some rocks from the 2018 diggings also fluoresce a bright lime green but there is no visual indication of autunite. Presumably it is a uranyl ion in some form, but it isn't clear what that form is. Examples include quartz and feldspar with irregularly shaped zones of fluorescence. In the quartz it was concenrated in areas of internal fracturing.
Metatorbernite - Cu(UO2)2(PO4)2·8H2O
A single crystal cluster of metatorbernite was found by Don Doell at Governor Lake. The cluster is pale green and less than 1 mm across. A photo and analysis of the specimen can be found here, on the U. Arizona RRUFF website. Another copper mineral, covellite, is also found at that location, though not in direct association with the metatorbernite.
Doug Wilson found a single specimen at Bayer's Lake with a couple 1 mm plates. There are no crystals of other species on the piece, but just some dark greasy staining. This piece has not been tested, but shows the typcial green color of metatorbernite and does not fluoresce, as autunite would do.
Microcline - KAlSi3O8
Microcline (or orthoclase - I don't know how to distinguish the two) crystals are common. Along Highway 103 they are frequently smooth-faced and orange to pink in color. At Bayers Lake some of the crystals reached 10 cm in size. Some show several forms making them interesting for crystallographic purposes.
The feldspar crystals were frequently Baveno-twinned. They tended to be heavily etched but made interesting specimens. The specimen below is a prism with a square outline. The twinning is clear when looking at the termination of the crystal, with growth/etching lines at or near 90 degrees. The twinning probably accelerated growth - this crystal is about 9 cm long.
Muscovite - KAl2(AlSi3O10)(OH)2
Books of muscovite, with a pseudohexagonal outline and often showing the star-shaped twinning, were fairly common. Specimens were generally poor to mediocre, but a few nice pieces were also collected that showed large crystals in good condition.
Natrojarosite - NaFe3(SO4)2(OH)6
A single example of this sulfate mineral was found in the rotten 2018 pod. It was identified using Raman spectroscopy; I hope to look at the chemistry with EDS/WDS in the future. It is a secondary mineral, likely formed after rotting pyrite.
Pinite
Pinite is a working term for pseudomorphs after silicate minerals - commonly muscovite after cordierite. Large (greater than 10 cm) pinites were found embedded in the granite at the Bayers Lake exposures. The best ones were found in the area exposed by the 2018 expansion. Because they are replaced with muscovite, they cleave very easily and are typically not terminated. The example below is posisbly unique for the area in being terminated. Some similar material from Governor Lake was analyzed by Don Doell and found to contain microscopic relic patches of cordierite and the much rarer sekaninaite. Sekaninaite is the iron analogue of cordierite.
Pyrite - FeS2
There are areas of iron staining in the rocks moved for the expansion started in 2018 through t present (2023), indicating weathered pyrite. The pyrite that I have seen seems to be well mixed with the other minerals. In the example shown below, it is intergrown with muscovite. The pyrite is granular and seems to have a spongey layered structure. No good crystals have been found to date.
Quartz - SiO2
The most prominent mineral from this area was smoky quartz. Good quality crystals were found, some suitable for cutting. Some of the crystals from Bayers Lake reached nearly football size, but were commonly 10 cm in length. Most are quite dark (var. morion) and have a breakdown product of feldspar adhered to the surface. Many also exhibit a clear or white overgrowth. The black quartz with a white overgrown was particularly attractive. The crystals from Highway 103 tend to be smaller but cleaner and nearly pitch black. Some of these were associated with autunite.
Many of the quartz crystals show interesting morphology, displaying more than the usual basic forms. Additional forms such as s{111}, x{511}, and steep rhombohedrons {301} and {501} have been identified from these crystals. The steep rhombs are steep faces that lie between the prism faces and the usual rhombohedral faces.
Some of the quartz from Bayers Lake is totally gemmy and free of veiling. This makes it suitable for faceting. While quartz is too soft to be a gemstone, it still makes very attractive cut stones. Some of the rough crystals can be quite large and look almost black in hand, but when viewed with strong backlighting, their clarity is apparent. When cut, the pieces are smaller, and designed to transmit and reflect light to the viewer, so they appears lighter and brighter than the rough.
In addition to the smoky quartz, amethyst has also been found in this area. The Canadian Museum of Nature has a couple specimens in their collection. One is a large pale crystal (CMNMC 47233) while the other is a deep purple vein section (CMNMC 47232). I would guess they were collected in the 1960s-70s. The labels say they were found when digging a "sewer & water trench opposite the Anglican Church, on the Old St. Margaret's Bay Rd., Timberlea". That places them from the northwest corner of the map area.
Schorl (Tourmaline) - Na(Fe2+3)Al6(Si6O18)(BO3)3(OH)3(OH)
Black schorl tourmaline was common at the Bayers Lake exposures. One 'pod' of friable schorl was found that was perhaps 25x25x10 cm in size. Terminated and even doubly terminated crystals have been found, but they are rare. Still, in my experience, they are the best formed tourmalines from Nova Scotia. A specimen was sent for EDS analysis in 2018 to confirm that these are schorl rather than the visually similar dravite, with which schorl forms a series.
Most shorl crystals in this area are lustrous and unweathered, but some that were collected around 2022-23 were quite the opposite. The pictures below show one crystal that has been altered to the point that it has a bit of a rusty brown color and is very porous. The pores contain microcrystals of secondary minerals, still to be identified. The second picture shows a hole through a partial crystal of quartz where a shorl crystal was altered to the point where it is completely gone. Tiny feldspar crystals are scattered on the inside of the hole.
Titanite - CaTi(SiO4)O
Titanite has been found as tiny pink sprays in a zone with pockety granite. I have not looked for it elsewhere. It was identified using Raman spectroscopy. Pink is an uncommon color for titanite. Studies on more deeply colored Italian material suggest the pink color reflects a high Mn/Fe ratio and that the Mn and perhaps the Fe are divalent, substituting for Ca rather than for Ti as is the case for other coloring mechanisms in titanite (Mottana and Griffen 1979). It would be interesting to compare those results and the Bayer's Lake material.
Zircon - Zr(SiO4)
Zircon is reported by collector Don Doell from Governor Lake. I believe the ID was using Raman spectroscopy.
Conclusion
The Bayers Lake - Timberlea area is interesting in that it has produced miniature to cabinet sized pegmatite specimens, which are otherwise rare from Nova Scotia. Highway building and other construction exposed all of the collecting areas and most are now collected out or built over. However, continued expansion of the city may lead to new, short-lived sites in the future.
Acknowledgements
Thanks to Doug Wilson and Andrew Macrae for their accounts of the now defunct Highway 103 overpass pegmatite and Terry Collett for use of his photos. Also thanks to Dino Nardini and Logan Robertson for allowing me to photograph their specimens, and to Don Doell and the University of Arizona for Raman identifications. Finally thanks to Doug Wilson for the gift of the Highway 103 TiO2, the torbernite , and the altered tourmaline specimens..
References
Allan, B. D., Clarke, D. B. (1981) Occurrence and origin of garnets in the South Mountain Batholith, Nova Scotia. The Canadian Mineralogist: 19(1): 19–24.
Messervey, J.P. (1933) Feldspar in Nova Scotia; Department of Public Works and Mines, Nova Scotia, Pamphlet No. 10 (NSDNR Rept 32/01): 10-14.
Mottana, A., Griffen, W.L. (1979) Pink titanite (greenovite) from St. Marcel, Valle D'Aosta, Italy. Rendiconti Societa Italiana di Mineralogia e Petrologia, 35(1), 135-143.
Nova Scotia Geology Map, Atlantic Geoscience Society, 1994.
O'Reilly, G.A. (2000) Mineral Occurrence Database, Nova Scotia Department of Natural Resources.
Schmedt auf der Günne, J., Mangstl, M., and Kraus, F. (2012) Occurrence of Difluorine F2 in Nature - In Situ Proof and Quantification by NMR Spectroscopy. Angewandte Chemie International Edition, 51(31), 7847–7849.
Wallace, P. (1998) Bayer's Lake Business Park. in Discovering Rocks, Minerals, and Fossils in Atlantic Canada: A Geology Field Guide to Selected Sites in NF, NS, PEI, and NB. Atlantic Geoscience Society Special Publications, 118-120.
Disclaimer: This page is intended for information purposes only. The locality is not necessarily open to collecting. The locality is not necessarily safe.