The Different Types of Slate and Their Unique Characteristics

By Anna Lockhart. 

Do you know what determines the kind and color of different natural slates?  

How does slate form? A microcrystalline metamorphic rock, or slate as we commonly call it, is made from the sediments and silts that settled on the seafloor over 400 million years ago. Due to the perfect storm of weather and temperature conditions of the ocean water over time as the ancient ocean turned to modern land, those sediments were molded and turned into the slate beds where modern miners find the material so commonly used in roofing, flooring and countertops.  

Natural slate can come in a variety of beautiful colors. The chemicals and minerals present in the clay and sediments at the time of the slate’s formation determine the color of the resulting slate. For example, slate that is red in color is due to the unusually high amount of iron dioxide or hematite in its composition.  

Similarly, because each geographical region has unique chemical compounds in the soil and water, certain colors may also be more common in particular regions. North American slate beds produce a variety of colors depending on which geographical region you are digging in. Some regions have their own particular colors that are unique to that region alone, like the Vermont Gray slate, which is notable for its clear-gray color and signature black speckling that fades to a brownish tone as it is exposed to the elements over time.  

Like many materials used in roofing, natural slate is not immune to fading with weathering over time. Most natural slates go through weathering and will change color or tone the longer it is exposed to weather conditions. This is important for homeowners and contractors to keep in mind when deciding on a color scheme and roof materials.  

Natural slate is a great option for roofing projects and can be shaped into a variety of shingle designs and thicknesses. With the naturally occurring weathering that happens to the color and tone of these materials over time, slate shingles provide a unique opportunity to mix and match the slate types to create a mosaic style roof. The possibilities are truly endless!  

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About Anna  

Anna Lockhart is a content administrator/writer for RoofersCoffeeShop®, MetalCoffeeShop™ and AskARoofer. When she’s not working, she’s most likely to be found with her nose in a book or attempting to master a new cookie recipe.