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
- Slate's foliaceous structure enhances its flexibility
and its resistance to impacts, better than ceramic tiles,
- Slate is inert to acids.
- Because it contains no pyrite,
slate is unalterable.
- Free of internal oxides, slate resists
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.