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Celebrating local red sandstone


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History for the Curious with John G. McKay

In 1889, when the Catholic congregation of Amherst built St. Charles Church, the foundation was laid using the first stone quarried from the Amherst Red Stone quarry, east of Willow Street. This operation, managed by partners James Donalds, a prominent Amherst butcher who owned the land, and John McKeen, manager of the Bank of Nova Scotia, was to supply general building stone throughout the area for the next 25 years.

Over the years this stone has proven to be of such poor quality for aboveground construction that many of the local buildings constructed with it just over a century ago and later, are showing signs of dangerous deterioration, both structurally and aesthetically.

Geologically this New Red Sandstone, which underlies a major portion of the Isthmus of Chignecto, is extremely vulnerable to the elements; its principal shortcoming being that it is not water proof.

In a climate less severe than ours it might stand up fairly well. However, its capacity to absorb water leads to surface spalling when this moisture freezes, causing the stone to literally slough away, with each succeeding winter taking its toll.

 A comparison between any of the red stone buildings and the grey sandstone of the old (1936) Amherst Post Office, now Town Hall, reveals a comparatively stable surface and structural soundness in the latter stone, in contrast to the soft, almost mud-like surface of the former.

The grey stone, quarried in Wallace, Nova Scotia, was laid down twelve or fifteen million years before the New Red sandstone began to overlay the coal measures deposited during the Upper Carboniferous Period some 310 million years ago.

While a dozen million years may not seem very long in such a vast time span, it was long enough to allow clay and silt to be leached from the sediments forming the grey rock, and time enough for the forces of compression to bond its granular structure to an impervious consistency.

As well, most sedimentary rock tends to undergo an additional hardening process upon exposure to the open air, much like the curing of concrete.  This process seems to be extremely limited or non-existent in the red stone, further reducing its ability to withstand shear or torsion stress.

The costly cosmetic work carried out on several Amherst buildings in recent years will only temporarily delay the inevitable unless some process for sealing the surface from water absorption and the acidic effect of the modern urban atmosphere was incorporated into the work; there is no evidence that it was.

Even at two dollars a ton, the going price for stone from the Donalds quarry over a century ago, one should hope for something more than a hundred years or so of useful life from our public buildings. After all, the stone for the Egyptian pyramids was quarried nearly five thousand years ago, and shows every sign of holding things up for a long time yet.

 

John G. McKay's history column appears periodically in the Amherst News. He has written several short novels that he sells every Friday at the Amherst Farmer's Market.

 

 

 

 

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