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Slate Information

About Slate

It has a very distinct look and is used for a variety of applications. Natural slate has been used for building architecture for several hundred years; if not longer. In this article we will take a look at this incredible natural stone and its use in building construction since perceiving differences between natural and man made materials takes a bit of effort. Additionally, we will discover what makes it differ from other materials. Finally we will briefly consider how to work with it and what steps can be taken to care for and maintain natural slate.

What is Slate?

Slate is natural metamorphic rock that is distinct and very identifiable once you have seen it and learned what it is. It might surprise you to learn that slate was at one time mud in the ocean. Notice the following description of slate by a geologist in an article written for UseNaturalStone.org

Slate is a metamorphic rock. It starts out as marine mud, composed of clay, silt, and organic material that settles to the bottom of the cold, dark, ocean.

But how does it go from a pile of material to a slate? Well it first becomes a different rock called shale (a sedimentary rock). However, something amazing happens that transforms the shale into slate. The same article referenced above says the following:

But sometimes a layer of seafloor mud becomes trapped in a collision between continents... ...the whole region crumples together, causing the rocks to become bent and folded, buried more deeply, and heated. This metamorphic process does not melt the shale. Instead, compression re-aligns the flat mineral grains, giving the rock a pronounced linear texture that often is at right angles to the original sedimentary layering. As the rock heats up, the minerals recrystallize and grow into each other...

The tremendous pressure and heat transforms shale in to slate. Slate is a material with very interesting properties that make it very useful. Let's look at some of those now.

Slate's Properties

One of the interesting properties of natural slate is that it is non-porous. That means that it is so compressed that liquids cannot penetrate the surface of the material. Most natural stones have some degree of porosity, but not slate. This is beneficial for some uses as we will see in a bit.

Slate is also limited in color. It is usually a gray or greenish grey color but it also forms in other colors as well. Some other colors of slate are:

  • Black
  • Brown
  • Maroon
  • Green
  • Purple

Slate's color is influenced by the marine environment from which it was formed. Nonetheless, most slate is gray in color.

Slate is also a hard stone registering at 5.5 on the Mohs scale. That is just slightly over the halfway point of the scale so it is on the hard side fo the scale, although not by much. Just for comparison, granite ranges from 6 to 7 on the same scale.

Uses For Natural Slate

Slate has a few very practical and durable uses. For example, slate is very practical when used as roofing tiles. Slate works well as a material for shingles because it it is durable, holds up under temperature change, and does not absorb moisture like other stone does. So it works well for roofing tiles.

Slate is also great for fashioning floor tiles. For much the same reason as we just mentioned, slate flooring is very nice and is durable as well. Additionally, slate is good for paving and other outdoor hardscape uses.

Cutting Slate

When working with slate it is recoemmended that a diamond blade be used. Knowing which kind of blade is one key to good results. Using a diamond blade for cutting hard stone like slate is recommended. Also, we recommended wet cutting and wearing PPE since slate can have a tendency to spall when cutting.

Care and Maintenance

Regular cleaning of a slate surface is the most effective way to care for and maintain the natural beauty of the surface. A normal slate cleaning routine using the following steps is effective:

  1. Sweep the dust up from the surface. During the first few months after installationm skate goes through a "spalling" period where small pieces flake of the stone. This is normal nad should stop after a few months. Sweeping removes dirt from the surface.
  2. Using a soft cloth or mop, wipe the floor after soaking the mop or cloth in a mild detergent mixed with warm water.
  3. Dry using a clean, dry cloth and allow to air dry overnight.

As we have senn in this article. Slate is an impressive and practical material that has some very handy applications. Knowing a little about working with it and how to care for this distinctive stone is helpful to those working on slate or those that own a slate surface.