History –Canadian Slate

Slate is extracted from fine clay mud that has accumulated at the bottom of primeval oceans. During the formation of mountain ranges, the pressure exerted crushed this clay layer, compacting it and making the rock less porous with a stronger cohesion. In Canada, conditions favourable to slate formation are found in several places in the Appalachian Mountains, from the Eastern Townships to Newfoundland.

Here are the major qualities of Canadian slate:

• Slate's absolute impermeability makes it resistant to freezing
• Slate's foliaceous structure enhances its flexibility and its resistance to impacts, better than ceramic tiles, in fact.
• Slate is inert to acids.
• Because it contains no pyrite, slate is unalterable.
• Free of internal oxides, slate resists delamination.

By contrast, because the internal structure of slate extracted from warm seas contains large quantities of iron oxide, it is greatly porous and subject to constant delamination.