Introduction
The term 'Coal Measures' is a historical one referring to the strata of the Carboniferous period (approx. 360-300 mya). This page is focuses on the minerals found at the several coal mines in the province and related rocks. This article is unlike the others in this website because I have NOT visited most of these sites, with the exception of Melmerby Beach. The article is mostly a brief review of several papers in the literature, with a few photos added. While efflorescent sulfate minerals are generally of little interest to collectors, I wanted to include this page because the suite of minerals from the coal mines is amazing and some of them are quite rare. These mines provided the first samples of blödite and tamarugite in Canada.
History
Coal mining was a critical industry in Nova Scotia for hundreds of years. In 1720, coal was first produced in what is now Canada using regular mining methods on the north side of Cow Bay, Cape Breton, Nova Scotia. Numerous mines in Cape Breton, as well as Pictou and Springhill provided energy for the province and were vital for iron mines in Bridgeville, Londonderry and elsewhere. As with the gold mining history, there are countless books about coal mining in the province. I will not attempt to repeat the history of the mines here. A very nice background, available online, is given by Calder et al. (1993).
Geology
Rocks include several groups of similar age (roughly 300-320 million years) such as the Morien Group in Cape Breton, the similarly aged Cumberland Group at Springhill, and the slightly younger Pictou Group at Melmerby.
Mineralogy
Generally, the sulfates are formed as a post-mining secondary minerals inside the coal mine. Zodrow reports that the species can be distinct between mines, localized within a mine, and are even seasonal. Some specimens were found at outcrops outside of the coal mines, but these require several weeks of dry weather to form, produced minute samples and tended to be contaminated / mixed (pers. comm. E. Zodrow). Blooms in the mines reached up to several meters across.
Specimens of the sulfates now reside in a number of locations including in Paris (Musee Nationale), Smithsonian Institution, Michigan State, US Steele (Morgantown), Spain (Zoragossa), Netherlands, Ottawa (Ontario, Canada), and Queen's (Kingston, Ontario, Canada) (pers. comm. E. Zodrow).
Table 1: Minerals reported from the coal measures of Nova Scotia.
Alunogen - Al2(SO4)3 · 17H2O
Hoffman (1880) reports on material
"collected by Mr. Scott Barlow from an old heap of shale at the 'Scotia Mine', Springhill coal-field, Cumberland County. The specimen was in the form of a crust of from five to five and a half centimeters thick. Colour white, in some places light yellow. Taste inky-astringent. Melts in its water of crystallization and at a higher temperature gives off sulphuric acid. Soluble in water."
Bonardi and Traill (1975) list an X-ray diffraction pattern entry (XRD Pattern 019) of alunogen from Springhill in the national database.
Epsomite - MgSO4 · 7H2O
Zodrow and McCandlish (1978) reports epsomite from the 1B mine, Glace Bay, as white fibers to 3-4 cm. It is localized to the roof of the coal seam, associated with quartz, and not on the coal face. It is also not associated with melanterite.
Halotrichite - FeAl2(SO4)4 · 22H2O
Hoffman (1880) reports halotrichite from Glace Bay. Zodrow and McCandlish (1978) say it also occurs in surface outcrops of the Emery seam with pickeringite and aluminocopaite. Surface occurrences are short lived, completely dissolving in heavy rains. Zodrow et al (1979) write that it forms at the 1-B mine, on the roof sandstones above the Phalen coal seam, as silky, fibrous crystals to 1.5 cm, with a greenish tinge at the base. Here it is associated with epsomite. At another, nearby, location in the mine, it forms small amber-colored spherical masses.
Melanterite - Fe2+(H2O)6SO4 · H2O
This species was first reported by Gilpin (1885) from Glace Bay who says it is not uncommon. Zodrow and McCandlish (1978) say is occurs with sideronatrite and epsomite in curved fibers to 3 cm in length. Zodrow et al (1979) add that during a revisit to the 1-B mine they discovered that melanterite from a previous visit had altered almost completely to fibroferrite. In a similar manner, melanterite at the Stubbart coal seam of the Prince Mine had altered to aluminocopiapite.
Rozenite - FeSO4 · 4H2O
Reported from the Prince Mine, Point Aconi as white and powdery (Zodrow and McCandlish 1978). Also found on surface outcrops of the Stubbart seam, and in outcrops of the Phalen Seam, Glace Bay.
Sideronatrite - Na2Fe(SO4)2(OH) · 3H2O
Zodrow and McCandlish (1978) note that sideronatrite forms as a fibrous crust on coal and is stable in surface conditions. They also note it can be confused with jarosite, and that other reports of jarosite are possibly also sideronatrite. Zodrow et al. (1979) report that it was also found at Point Aconi at a surface coal-seam outcrop.
I was alerted to an unknown yellow mineral at Melmerby, Pictou County in a outcrop on the shore. The first picture of this article shows mineralization forming from weathering coal. The mineralization is yellow to orangish-yellow and based on testing, seems to be essentially all one species - sideronatrite. Tests performed include EDS, XRD, and Raman. It was also verified that it does not dissolve in water at room temperature.
In many cases, including this one, sideronatrite formation obtains the essential sodium from seawater. Thus it is frequently found near the sea shore. Mindat.org notes that it reversibly dehydrates to metasideronatrite, Na2Fe(SO4)2(OH)·H2O, depending on relative humidity and exposure to sunlight.
Unknown
White wispy sprays of the most delicate needles, growing on sideronatrite. Possibly ferrinatrite based on chemistry and visual similarity, but this has not been tested yet.
Conclusions
The coal mines have produced an amazing suite of ephemeral sulfate minerals. In many cases, these have not been reported from elsewhere in the province. While amateur collectors won't be allowed access to the coal mines, these rocks also outcrop along the water and other places, providing places to search for these minerals.
Acknowledgements
Thanks to curator Tim Fedak and the Nova Scotia Museum of Natural History for allowing me to photograph specimens from the collection and share those pictures.
References
Bonardi, M., Traill, R.J. (1975) Catalogue of X-ray diffraction patterns and specimen mounts on file at the Geological Survey of Canada. Geological Survey of Canada Paper 75-8.
Calder, J.H.; K.S. Gillis, D.J. MacNeil, R.D. Naylor and N. Watkins Campbell (1993) One of the Greatest Treasures, The Geology & History of Coal in Nova Scotia. Nova Scotia Department of Natural Resources, Information Circular No. 25. [Online 2018]
Gilpin, E. (1885) Feather-alum (Halotrichite) from Glace Bay, Cape Breton. Proceedings and Transactions of the Nova Scotian Institute of Natural Science: 6(3): 175-179. [Online 2018]
Hoffmann, C. (1880) Chemical Contributions to the Geology of Canada from the Laboratory of the Survey. Geological Survey of Canada.
Zodrow, E.L., McCandlish, K. (1978) Hydrated Sulfates in the Sydney Coalfield, Cape Breton, Nova Scotia. Canadian Mineralogist: 16: 17-22. [Online 2018]
Zodrow, E.L., Wiltshire, J. and McCandlish, K. (1979) Hydrated Sulfates in the Sydney Coalfield, Cape Breton, Nova Scotia. II. Pyrite and its Alteration Products. Canadian Mineralogist: 17: 63-70. [Online 2018]
Zodrow, E.L. (1980) Hydrated Sulfates from Sydney Coalfield, Cape Breton Island, Nova Scotia, Canada: The Copiapite Group. American Mineralogist: 65: 961-967. [Online 2018]
Zodrow, E.L. (1989) Summary report of secondary sulphate minerals, Sydney Coalfield, Nova Scotia, Canada. Nova Scotia Department of Mines & Energy, Report 89-3, Mines & Minerals Branch Report of Activities, Part A: 141-143.
A history of coal mining in Nova Scotia. Nova Scotia Department of Mines, Information Series No. 2, 1978. [Online 2018]
Disclaimer: This page is intended for information purposes only. The locality is not necessarily open to collecting. The locality is not necessarily safe.