Slate is a popular stone that has many practical applications, including things like slate flooring and slate countertops. But you may be wondering what is slate exactly?
Slate is, by definition, a fine-grained, foliated metamorphic rock. This means that slate comes from another kind of stone, known as shale, a sedimentary rock that is made predominantly of clay. When shale is exposed to certain conditions, such as volcanic ash, slate can form. However, slate is most often formed around a tectonic environment. Shale and mudstone in sedimentary basins become compressed as tectonic plates shift. The force of the pressure and heat exerted upon the mud and shale will modify the clay particles. Foliation then occurs due to horizontal compression.
Minerals often found in slate include chlorite, pyrite, biotite, muscovite, and quartz. Sometimes, it will even contain small quantities of tourmaline, zircon, magnetite, and feldspar. Slate is incredibly smooth and durable because of how it is formed. Presently, the majority of the world’s slate comes from mines in Spain, China, Brazil, and throughout the United States. You may have even heard of Vermont slate or Indiana slate.
Current applications of slate include roofing, slate flooring for indoors and outdoors, cladding, landscaping, slate countertops, and even as elements in furnishings like chalkboards, tabletops, and billiard tables. The reason slate is used is due to it being highly resistant to damage, including acid spills and fire.
Slate floors, for example, are seen everywhere, as porches and patios, in finished basements, kitchens, and bathrooms. Interior slate flooring is available in a number of colors that come from the natural coloring and patterns—also known as the natural cleft—including swirls of green, blue, red, purple, black and gray. Slate is also an excellent alternative to granite and marble, because the stone is non-porous. This means that you do not have to worry about staining or countertops and floors that harbor bacteria. Liquids will not absorb into slate.