How Much Heat Can Slate Handle?

Heat Tolerance

• Slate countertops do not scorch, char or discolor if you set hot pots and pans on them. In fact, it is so resistant to heat, you can build fireplace boxes and hearths from slate and indefinitely build fires in the fireplace with no chance of the slate cracking or breaking.

Slate Formation

• Slate is a metamorphosis of clay and shale created on the beds of ancient seas by a combination of pressure and heat applied to the shale and clay over thousands of years. This process, called foliation, aligns the minerals in different directions, forming thin layers of rock that adhere together from the constant pressure. Some slate has natural decorative patterns embedded on the surface, formed by plant and animal fossils. If you have the good fortune to find slate with these natural designs, use them as a focal decorating point in your stone project. The hardness of slate depends on where it is mined. The hardest slates come from the United States, United Kingdom and Canada.

Slate Classification

• The two general classifications of natural stone are siliceous and calcareous. Slate, along with granite, quartzite, sandstone, bluestone and brownstone is siliceous, which means it largely is composed of silica. Silica is a substance in sand used to make glass, which contributes to its durability. Calcareous stone is softer and more delicate, as its main component is calcium carbonate, an ingredient found in paint, toothpaste, antacids and cement. Common kinds of calcareous stone used in home decor include limestone, marble, travertine and onyx.

Other Slate Benefits

• Besides being extremely heat tolerant, slate is impervious to acids found in many cleaning products, citrus juice and alcohol, making it a superior choice for kitchen counters and floors. Although slate easily scratches, the marks can be buffed out with fine-grit sandpaper or mineral oil. Some homeowners like the scratches and feel they add to the rugged character of the slate. Slate is nonporous, so it does not absorb liquids. Slate does not require sealing.