142 20.2 Industrial Materials — Physical Geology – 2nd Edition

Figure 20.2.1 Sand and gravel in an aggregate pit near Nanaimo, BC.

Approximately 80 million tonnes of concrete are used in Canada each year—a little over 2 tonnes per person. The cement used for concrete is made from approximately 80% calcite (CaCO₃) and 20% clay. This mixture is heated to 1450°C to produce the required calcium silicate compounds (e.g., Ca₂SiO₄). The calcite typically comes from limestone quarries like the one on Texada Island, B.C. (Figure 20.2.2). Limestone is also used as the source material for many other products that require calcium compounds, including steel and glass, pulp and paper, and plaster products for construction.

Figure 20.2.2 Triassic Quatsino Formation limestone being quarried on Texada Island, B.C.

Sodium is required for a wide range of industrial processes, and the most convenient source is sodium chloride (rock salt), which is mined from evaporite beds in various parts of Canada. The largest salt mine in the world is at Goderich, Ontario, where salt is recovered from the 100 m thick Silurian Salina Formation. The same formation is mined in the Windsor area. Rock salt is also used as a source of sodium and chlorine in the chemical industry to melt ice on roads, as part of the process of softening water, and as a seasoning. Under certain conditions, the mineral sylvite (KCl) accumulates in evaporite beds, and this rock is called potash. This happened across the Canadian prairies during the Devonian, creating the Prairie evaporite formation (Figure 6.2.8). Potassium is used as a crop fertilizer, and Canada is the world’s leading supplier, with most of that production coming from Saskatchewan.

Figure 20.2.3 Slate used as a facing material on a concrete building column in Vancouver.

Another evaporite mineral, gypsum (CaSO₄.2H₂0), is the main component of plasterboard (drywall) that is widely used in the construction industry. One of the main mining areas for gypsum in Canada is in the Milford Station area of Nova Scotia, site of the world’s largest gypsum mine.

Rocks are quarried or mined for many different uses, such as building facades (Figure 20.2.3), countertops, stone floors, and headstones. In most of these cases, the favoured rock types are granitic rocks, slate, and marble. Quarried rock is also used in some applications where rounded gravel isn’t suitable, such as the ballast (road bed) for railways, where crushed angular rock is needed.

Media Attributions

• Figures 20.2.1, 20.2.2, 20.2.3: © Steven Earle. CC BY.

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