Introduction

With uses ranging from keeping the roads free of ice in the winter, to seasoning our food, salt is an important commodity. Nova Scotia is able to supply its salt needs thanks to a pair of working mines, and in the past by a third, now closed, mine. On occasion these mines have produced interesting mineral specimens. The three mines, located at Malagash, Nappan, and Pugwash (all in Cumberland County) are considered as a group in this article. Nova Scotia also has small amounts of potash, containing minerals such as carnallite and sylvite.

History

The first salt mine in Nova Scotia was at Malagash. Exploratory drilling began after salt brine was discovered in a water well in 1912, at a depth of 80 feet. In 1917, drilling began do determine the size of the deposit. In 1924 Malagash Salt Products Ltd. was formed and began operations. They reorganized into the Malagash Salt Company Ltd. in 1927. In 1951 the mine was bought by the Canadian Salt Company and they operated the site until 1956. At that time transporation and operating problems forced the closure of the mine. A nice collection of images from the Malagash Mine are available online from the Nova Scotia Archives (https://novascotia.ca/archives/search/?q=malagash). For visitors to the area, there is a small museum remembering the Malagash Mine (http://www.novascotia.com/see-do/attractions/malagash-salt-mine-museum/1485).

The second mine was discovered by Imperial Oil Limited in 1931, while performing exploratory dilling for oil at Nappan. Beginning in 1947, Maritime Industries Limited produced salt through the use of brine wells. The Nappan site is still in operation as of 2019.

Upon closure of the Malagash mine, operations were transferred to a site at Pugwash in 1959. Salt in significant quantities was discovered here in 1953 (Rose 1987). In the following decade production increased significantly from 100,000 tonnes to 800,000 tonnes. This mine also remains open today, producing about one million tonnes of salt a year.

Geology

In the Carboniferous, about 350-335 million years ago, Nova Scotia lay near the equator and much of the province was under water, covered by the Windsor Sea. The climate was very hot and dry, leading to evaporation of the inland sea. Today we see evidence of this sea in the extensive deposits of limestone, gypsum, anhydrite, and salt found in the province.

The solubility of the different minerals determined when they precipitated out of the saturated seawater. Hence the gypsum/anhydrite beds are overlain by halite which are further overlain by potash. There are a few reports of potash in Nova Scotia, but much more extensive deposits are found only a few hundred kilometers away at Sussex in the neighboring province of New Brunswick (same formations).

Mineralogy

The salt and overlying potash layers contain a number of other minerals. These are listed by Beohner (1986) as coming from an earlier unpublished report. The major rock forming minerals are listed as halite, anhydrite, and carnallite. Lesser amounts of sylvite, barite, calcite, gypsum, magnesite, polyhalite, pyrite and quartz are reported. Trace amounts of aegerine (a.k.a. acmite), boracite, celestite, chlorite, glauberite, goethite, muscovite, riebekite, rinneite and talc are reported. Unconfirmed trace species include illite, marcasite and prehnite. Goodman also reports bassanite, fluorite, pyrite, and lazurite from Nappan. Rose (1987) mentions, from earlier reports by Carter, sulfur and danburite. Chambersite is known from museum specimens.

Table 1: Minerals reported from the salt deposits of northern Nova Scotia.

I believe the reports listed here are the first reports of several minerals in Nova Scotia. The minerals include lazurite, aegirine, polyhalite, bassanite, boracite, and rinneite. This webpage is the first report of chambersite.

Bassanite - CaSO₄·0.5H₂O

While chemically similar to gypsum (CaSO₄·2H₂O) and anhydrite (CaSO₄), bassanite forms under much more restricted conditions and is much rarer. Goodman discusses the mineral and its formation in some detail, calling the mineral hemihydrate. It was identified from the upper 300 meters of the Sunoco 1A well boring at Nappan. It formed "small white or buff-colored grains having fibrous or platy habit" and was found "replacing gypsum or anhydrite along the crystal edge in any percentage up to complete substitution". Identification was by optics and powder X-ray diffraction. Goodman gives evidence for it being natural and not formed from the drilling process. He spectulated that the origin was due to hot spring action, possibly from the Triassic volcanism that formed the Bay of Fundy basalts.

Carnallite - KMgCl₃·6H₂O and
Sylvite - KCl

Carnallite, and to a lesser degree sylvite are the two main components of the potash that overlays the halite in pods. No crystals are reported but they may certainly exist. The Nova Scotia Museum of Natural History still has a few rare early specimens from the Malagash mine.

Chambersite - Mn²⁺₃B₇O₁₃Cl

Chambersite is an insoluble borate mineral and the manganese analogue of the more common mineral boracite. The one shown below is a 1 cm pseudo-tetrahedron, with excellent sharp edges. The color is a deep amethyst-purple. It is a single specimen from the collection of the Fundy Geological Museum. Talking to the mine engineer/geologist at Pugwash has confirmed the locality as Pugwash; the specimen was found many years ago during a mine survey. A number of other smaller crystals (to a few millimeters) were found, but no other specimens are available. Chambersite is rather rare in good specimens worldwide; being reported from only about a dozen localities (MinDat 2014). The crystal below ranks as one of the finest known in the world in terms of crystal size, quality, and color.

At room temperature chambersite is orthorhombic. On the other hand the crystals exhibit an isometric form (tetrahedron). The change of the structure from isometric to orthorhombic occurs at 407° C. Thus the crystals were formed at a temperature higher than that and when the temperature dropped the atoms reorganized themselves in an orthorhombic symmetry. This is called a paramorph.

The color of chambersite is said to be caused by slight oxidation of the manganese. The purple color deepens with exposure to sunlight. Synthetic chambersite is colorless.

One more interesting fact about the mineral chambersite, though admittedly very technical, is that it is one of only two known natural multiferroic substances. The other mineral is congolite, the iron analogue of chambersite and boracite. A crystal that is multiferroic exhibits at least two of the following properties: (anti)ferromagnetism, ferroelectricity, and ferroelasticity. Synthetic multiferroics may play important roles in future generations of electronic or optical devices due to these rare physical capabilites.

Danburite - CaB₂SiO₄₂

Small nodules of danburite, up to 1 cm in size, occur in one of the units of anhydrite, found on all levels of the mine (Rose 1987). They are spherical to colliform in shape and consist of fine grained crystal aggregates. They are porcelain white to light gray. Identification was made using X-ray diffraction (Rose 1987 cites Carter 1985).

Halite - NaCl

I am not aware of any naturally occurring, pre-mining halite crystals from the mine. While halite is typically colorless, blue specimens are known from the Pugwash mine. The blue color is thought to be due to natural radiation that causes submicroscopic particles of sodium metal to form within the halite. The orange material is due to hematite impurities.

Evans (1970) discusses a drillcore drilled near Wallace, at 45 deg 46.9' N, 63 deg 23.8 W. It contained halite and sylvite, and minor carnallite, talc, quartz and hematite. Of special interest here, he describes hexagonal pseudomorphs of halite after carnallite (with sylvite as an intermediate stage). Those pseudomorphs were grains to roughly a millimeter in size.

Lazurite - (Na,Ca)₈(Al₆Si₆O₂₄)(S,SO₄,Cl₂)

This blue mineral (lapis lazuli is lazurite with pyrite) is reported by Goodman from a drill core, taken from Nappan, at a depth of 1250 m. It was in contact with altered limestone and formed small grains. This is the only report of the mineral from Nova Scotia that I am aware of.

Magnesite - MgCO₃

Rickaby (1923) describes magnesite crystals from the Malagash deposit as

"mostly prismatic, sometimes thick tabular, with a maximum length of five millimeters and a diagonal width of three millimeters....In colour they are grey to brownish, sometimes almost colourless, transparent to translucent, with a vitreous lustre. They have perfect cleavage parallel to the rhombohedral face r."

Conclusion

These deposits have thus far yielded a only few interesting specimens. However, there is potential for these mines to produce many more interesting minerals. The Pugwash and Nappan mines are still in operation. A small museum remembers the Malagash Mine.

Acknowledgements

Thanks Ken Adams and Kathy Goodwin from the Fundy Geological Museum for permission to take and use the chambersite photo, to the N.S. Dept. of Natural Resources and the National Archives for the historical photos, to Michael Rygel for the use of the photo of colored halite. Finally, thanks to the Nova Scotia Museum of Natural History for allowing me to photograph and use the photos of carnallite and potash.

References

Salt in Nova Scotia, Nova Scotia Department of Natural Resources, Mineral Resources Branch, Information Circular ME 33, 1992.

Mineral Spectroscopy Server, California Institute of Technology (http://minerals.gps.caltech.edu/COLOR_Causes/Radiate/)

Boehner, R.C. (1986) "Salt and Potash Resources in Nova Scotia", N.S. Dept. Mines and Energy, Bulletin 5.

Chambers, A.R. (1924) "The Salt Deposits of Malagash, Nova Scotia", The Transactions of the Canadian Institute of Mining and Metallurgy and the Mining Society of Nova Scotia, pg. 248-257.

Cole, L.H. (1919) "Notes of a Discovery of Rock Salt in Nova Scotia", The Canadian Mining Journal, vol. 40, pg. 8-9. [Online 2015]

Cole, L.H. (1930) "The Salt Industry of Canada", Canada Department of Mines, no. 716. [Online 2019]

Evans, R. (1970) "Genesis of sylvite and carnallite bearing rocks from Wallace, Nova Scotia", Third International Symposium on Salt, Volume One, Northern Ohio Geological Society Incorporated, Cleveland, Ohio, pg 239-245. [Online 2019]

Goodman, N.R. (1957) "Gypsum in Nova Scotia and its Associated Minerals", Geology of Canadian Industrial Mineral Deposits.

Grantham, R.G., (1985) "Index of the Nova Scotia Museum Economic Minerals Collection", Nova Scotia Museum Curatorial Report Number 52. [Online 2015]

Honea, R.M. and Beck, F.R. (1962) "Chambersite, a New Mineral", American Mineralogist, vol. 47, no. 5, pp. 665-671. [Online 2012]

Rickaby, H.C. (1923) "The Mineral Association of the Salt Deposits at Malagash, N.S.", University of Toronto Studies, Geological Series, no. 16, p. 46-52.

Rose, Peter A. (1987) "Petrography and Geochemistry of Anhydrite Units from the Canadian Salt Company Mine, Pugwash, Cumberland County, Nova Scotia", unpublished B.Sc. Honours Thesis, Dalhousie University. [Online 2019]

(to get) Aumento, F. (1964) "Authigenic Minerals and Preliminary Investigations of the Evaporite Deposit at Pugwash, Nova Scotia", Nova Scotia Research Foundation, unpublished report 13-64, 39 p.

(to get) Carter, D.C. (1985) "Geology of the Pugwash Mine - A Progress Report", Program and Summaries, Ninth Annual Open House and Report of Activities, Nova Scotia Department of Mines and Energy, 47-49.

(to get) Carter, D.C., Boehner, R.C., Adams, G. (1988) "Sulphur in Nova Scotia: Geological setting of native sulfur occurrences in Nova Scotia", Nova Scotia Department of Mines and Energy, Open File Report 88-01.

(to get) Goodman, N.R. (1954) "The Geology of Nova Scotia Gypsum", Bull. Can. Inst. Mining Met., vol 47, no 502, pp. 75-80.

(to get) MacQuarrie, J.R. (1981) "Malagash Salt", North Cumberland Historical Society, Oracle Press, 109 pgs.

(to get) "Salt : The Canadian Story, The Pugwash Story", Canadian Salt Co., Ltd., Pugwash, N.S., 1990.

Disclaimer: This page is intended for information purposes only. The locality is not necessarily open to collecting. The locality is not necessarily safe.