Marble was quarried in Eskasoni, Cape Breton County, in the 1800s but exploration at the site in the early 1900s illustrates how difficult it is to find economically-viable mineral deposits.

Several small pits were dug around the 1870s on top of a hill, which rises about 600 feet above the Bras d’Or Lake. Specimens from the site received diplomas at the 1900 Paris exposition.

In the early 1900s, C. A. Meissner examined the property for the Dominion Coal and Steel Company, because marble is often used as flux in steelmaking to promote fluidity and remove impurities in the form of slag during the smelting process.

At that time, Hector G. Brown and associates controlled about 700 acres of land fronting onto the north shore of East Bay at Eskasoni.

Meissner sank a number of test-pits to see if the marble was suitable for use in the company’s steel plant. His exploration work found that the area had marble and various other types of rock in it, such that there was not likely a sufficiently large deposit of marble to make a quarry worthwhile. Instead, the marble was in separate pockets that made extraction uneconomical. One of the pockets was estimated to be 260x195 feet. The largest was believed to be 625x110 feet.

J. L. Marsters, who described himself as a “quarryman,” examined the site at Meissner’s request and concluded that “it would be, in my opinion, unwise to think of opening a quarry here. First, because the greatest width would not be sufficient to give us a working face sufficiently large to enable us to get out a large output economically, and the width being very small would bar any large amount of marble being there, unless the pockets enlarge greatly at depth.”

He went on to say that extracting from the top of the mountain, where the marble outcropped, would require an underground mine since much of the marble seemed to underlie another type of rock, felsite. In other words, shafts would have to be dug through the felsite to reach the marble underneath. Marsters advised against this saying, “This, in my opinion, would not be a wise move, as opening up a tunnel here would be extremely expensive….”

Meissner’s work also led to the conclusion that the marble deposit was likely not suitable for building or decorative stone. Hugh Fletcher of the Geological Survey of Canada report wrote, “Although some handsome material undoubtedly occurs, it does not seem to be sufficiently massive to permit its extraction in large blocks. Whether or not workable bodies occur remains for more serious exploration to reveal.” (In geology, massive does not mean large. It means rock that is homogenous and does not have different structures, like cracks and joints, within it. In this case, Fletcher meant the deposit would not likely produce the large, solid, attractive blocks of stone necessary for building.)

The marble in Eskasoni also contained some dolomite and serpentine. This gave it interesting colours, including green and yellow. It also contained many stringers and clouds of a dark blue-grey colour in which flakes and dots of glistening hematite (specular iron ore) could be seen.

Marble and dolomite are both metamorphosed limestone – they started as limestone but were turned into different rocks. Marble is pure limestone that was subjected to extreme heat and pressure that turned it into marble. By “pure” we mean the limestone was essentially pure calcium carbonate and did not contain a lot of impurities like quartz, clay, feldspar, micas, etc. Dolomite is limestone that has been chemically modified by magnesium-rich groundwater.

The Eskasoni marble is an example of how difficult it is to discover and develop mineral deposits. Only one in every 10,000 mineral exploration projects ends up being a mine because there are so many requirements that must be met to make a deposit viable (i.e. the size and quality of the deposit, the availability and cost of supplies and labour in the area, the price of the mineral and whether there are customers for it, infrastructure to transport it to market, availability of capital to fund the project, etc.).

Given how rare it is that a mineral deposit is economically viable, it is important that we develop them when we can, both for the materials they provide and the jobs and economic benefits they create.

It is also important to note that the assessment of these factors can change over time as circumstances evolve. For example, when a new use for a mineral is invented or its price increases, a deposit that was not previously viable may become so.

The East Kemptville tin mine in Yarmouth County is an example. It was the world’s largest tin mine for a while in the 1980s and 1990s but it closed due to a collapse in tin prices. It has the potential to be mined again because tin prices are higher now, and because the deposit also contains indium, a critical mineral that is used in things like touch screens and solar panels.

Despite some marble extraction having taken place in Eskasoni, and the recognition it got at the Paris exposition, the challenges with the deposit prevented any further extraction.

The Eskasoni marble deposit is similar to the stone in the historical Scotch Lake dolomite quarry, aka the George’s River quarry: