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Stone origins: Slate

This floor is technically older than the dinosaurs.

Slate is incredibly versatile, able to be used for a variety of applications around the home. Not only can this stone serve as the basis for flooring or countertops, as the National Slate Association points out, it can even be used for roofs.

Slate’s unassuming exterior belies its somewhat complicated origins. The story of how slate gets from the earth’s crust to your kitchen is a surprisingly convoluted one.

Slate and shale – two sides of the same coin

Slate is a metamorphic rock, which means it’s the product of the transformation of another type of rock entirely. In this case, the other rock happens to be shale.

Shale is a sedimentary rock that itself is the result of the silt and clay-size minerals being compacted together. We have a different, more common name for this today: Mud.

Once upon a time, the movement of the earth’s colossal tectonic plates put huge pressure on this mere mud when they collided, transforming it into what we now know as slate. This metamorphic process is known as ‘low-grade’, because it involves a relatively low amount of pressure and temperatures when compared with other metamorphic rocks.

Partly because shale is full of clay minerals, which are able to be divided into sheets, slate too tends to cleave into such sheets or slabs once it is crushed. The pressure of the folding of the earth’s crust pushed the various minerals, so they lay parallel and at the same angle to the direction in which the pressure was exerted.

The ancient origins of slate

It’s important to know that all of these processes happened a long time ago – around 500 million years before humans ever wandered the earth to be exact, during the early Paleozoic era.

As a result of these ancient processes, according to the Minerals Education Coalition, slate can now be found anywhere around the world where the continental crust has been compacted by the collision of tectonic plates. In the United States, this includes areas like eastern Pennsylvania and the Green Mountains of Vermont.

Of course, it’s unlikely your slate countertop will last another half-billion years. But in order to help ensure it survives for as long as possible, you’ve got to seal it. Products like Dry-Treat’s STAIN-PROOF Original™ or META CRÈME™ can help keep it free of stains and damaging liquids.

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