The United States of America is a wonderful place to live if you’re looking for a natural variety of slate colors to choose from. You should know the Slate Valley of New York and Vermont is the only place in the world where nature produces rare varieties of slate colors such as:
- Green
- Gray
- Gray Black
- Purple
- Mottled Green and Purple
- Red
The look of slate, especially on roofing applications, is loved around the globe, however only in America can these rare slate colors be quarried. This happens due to the chemical and mineral composition.
As a result, not only the color of the slate is affected, but the quality and durability as well. We will let you in all you need to know before selecting the right variety for you.
What is slate?
According to Geology.com:
“Slate is a fine-grained, foliated metamorphic rock that is created by the alteration of shale or mudstone by low-grade regional metamorphism.”
It’s a stone of great structural integrity and beauty and according to the National Slate Association, it has an indefinite life, possibly lasting for more than 300 years.
The mineral composition of slate varies significantly from place to place, however, the primary constituents of all varieties are white and black mica.
Due to its characteristics, it can be split into smooth sheets. Great strength and imperviousness make slate one of the most durable and versatile materials available.
Nomenclature of Slate Colors
You will notice slate color varieties are often preceded by the terms: fading, unfading, weathering, and non-weathering. So it’s important for us to find out what they mean, especially because people tend to misunderstand these characteristics a lot, while they mean completely different things.
Fading
The term fading refers to slates that after prolonged outdoor exposure exhibit a chalk-ashen residue. This chemical is the result of a chemical reaction associated with the release of calcium from the material, which weakens its integrity and reduces its life expectancy.
Unfading
Unfading slate tiles do not produce the chalk-ashen residue, even after prolonged outdoor exposure. You can expect unfading varieties to present a greater life expectancy.
Weathering and Non-Weathering
Now here’s an interesting thing to mention. Colored slate is never fading. However, it may weather with time due to the oxidation of it’s embedded minerals. This causes the color of the tile to change over time, often towards buff, brown, gray or tan tones.
This oxidation, however, doesn’t affect the structural integrity nor the life expectancy of a slate tile.
Based on the degree of color change over time we can classify colored slates into three groups:
- Weathering slate varieties will most likely change color
- Semi-weathering varieties may or may not weather, so you can expect roofing made of this type of slates to present a non-uniform appearance
- Non-weathering slate varieties will hardly change color.
It’s important that you understand that some slate tiles will always weather, what changes from variety to variety is the percentage of how many of them are likely to weather.
Origination
Since the location of the quarry is very relevant for understanding the quality of the slate variety, slate colors are often also preceded by the name of the city they come from.
Popular Slate Colors
Let’s talk about some common slate color varieties, we’re sure this will help you decide what you want for your roofing or flooring application.
Virginia Blue-Gray Slate
Presenting an interesting classic color, this slate variety is tough, durable and definitely a top-quality material. It adds a luster of attractive lights and shadows on roofs.
Vermont Slate
Vermont Slate is offered in many colors such as grey, black, grey and green, and green and purple. Slate from this location is lower in lime content and is available in both fading and non-fading varieties.
Pennsylvania Slate
Pennsylvania blue-gray is possibly the best-known option from this selection. This variety is also called Pennsylvania black. Quarries from this estate also offer interesting unfading options like unfading Pennsylvania gray and unfading Pennsylvania black.
Blue-Black Pennsylvania varieties are also interesting due to the fact that they get darker with sun exposure.
Unfading Red Slate
Unfading Red Slates are a very beautiful slate variety that can only be found in Washington County, New York.
Freak Slate Colors
Slates of other colors different from those we’ve mentioned here are called freaks! Not only they are rare, but it’s also even rarer to find them thinner than ¼”, which makes them usually not suitable for roofing applications.
Did you find the right slate color for your roofing or paving tiles? We hope you have, if you’re living in Florida you can consult Eagle Stones to find out which slate varieties are available for your project.
