Limestone is a porous rock often used safely in fireplace hearths. For this reason, it’s assumed to be an equally safe choice for fire pits. However, things that happen commonly outdoors but don’t tend to occur inside—such as rain—can be a potential safety risk. When rainwater falls on limestone, it’s absorbed into the rock itself. This presents the possibility of a dangerous combination of water and fire.
Available in a wide range of colors that include gray, white, red, and blue, sandstone rocks can work well in gardens and other exterior locations. The problem with putting them in fire pits is that they’re extremely porous, meaning they hold water on the inside well, and there’s the possibility of an explosion when they’re exposed to heat. Plus, these rocks don’t hold up well when exposed to heat for long periods, such as what’s common with a regularly used fire pit.
Don’t get us wrong, we love river rocks such as polished black river rock. These attractive, naturally formed landscaping features are ideal for use in many places. The downside when it comes to fire pits is that since these rocks spent several years resting at the bottom of riverbeds, they likely contain a lot of water deep within them. This presents the same dangers associated with the two types of rocks mentioned above.
Formed by the mix of hot volcanic lava and water, pumice is full of cavities. It’s also widely used for cleaning when there’s a need for extra abrasion and for smoothing out various surfaces. However, the cavities in these rocks are often filled with water, and the high heat in a fire pit could result in a potentially dangerous explosion.
These rocks are on the small side. The problem with the smaller size of pea gravel is that the rocks usually don’t heat up evenly, which could cause some problems with the flame in your fire pit. Pea gravel also has a tendency to pop when exposed to high temperatures.
Soapstone is unique among rocks in that it’s on the softer side. The main reason this is the case is because these rocks are a mix of various materials, including micas, carbonates, and amphiboles. In addition to being prone to holding water, soapstone is also not hard enough to stand up well to being used in a fire pit.
A volcanic rock, basalt is a mix of quartz, iron ore, and similar substances. It’s formed under extreme heat, which is why it has a darker hue. While attractive for other landscaping uses, basalt is generally not a rock you want in your fire pit. The main reason is because of the possibility of explosion with exposure to high heat due to the water that often accumulates inside.
For advice on how to properly use decorative rocks in your landscape, reach out to the experts at RS&P Rocks Stones & Pebbles, a premier landscape rock and supply superstore. We specialize in drought-tolerant landscaping materials, including a variety of colored river rock and Mexican beach pebble. To learn how we can help you enhance the character and beauty of your outdoor space, call us today at (866) 380-0770.