Everything You Wanted to Know About Fire Pit & Fireplace Lava Rocks, Fillers

Chances are good that if you have seen a fire pit or gas fireplace lately, including your own, it has some lava rocks in it. But why?

If you have ever wondered what the purpose is for these fireplace lava rocks and other materials you see on firepits and sometimes even grills, then the following information can shed light on why they are so common as well as the benefits they can provide.

Why Use Fireplace Lava Rocks or Fillers?

The simplest reason that people use lava rocks and fillers in their fireplace is that they complete the appearance of a natural log fire. Log fires tend to generate lots of ash and embers. While these elements make cleanup more difficult, they do lend a large amount of charm, enhancing the aesthetic sense of warmth a fire can generate.

In a gas fireplace, having just flames coming out of a burner element may feel underwhelming by comparison. That is why so many companies have created simulated “gas logs” as well as lava rocks and fillers, which all help recreate the image of a typical log fire but with far less mess and no set-up time.

Lava rocks, for instance, help fill the visual space while giving gas flames a temperature resistant media to burn through and against. Fireplace filler does the same thing, but these “ashes” can get red hot just like coals, completing the illusion for your fireplace.

They also have a practical purpose in that they help heat spread and radiate more evenly, delivering a fire experience with fewer cold spots.

What Are Lava Rocks and Fireplace Filler Made Out Of?

Like their name states, lava rocks are made from actual lava. Volcanic eruptions spew out tons and tons of rock and ash into the sky. Basalt is one of the most common types of rocks ejected during an eruption, and it can take many forms based on how it cools.

Most products sold as “lava rocks” are vesicular basalts, says Washington University in St. Louis. This type of rock forms when air bubbles get trapped inside lava as it cools and expands. Highly vesicular basalt rocks are often called pumice, but they are more delicate than the rocks you would typically buy for your fireplace or garden.

Fireplace filler is commonly made of a material called vermiculite. Vermiculite has an amazing property where it expands, or “exfoliates,” many times its original size when heated under high temperatures. Despite having a fluffy appearance, this state allows vermiculite to be extremely resistant to high temperatures. You may notice this effect when fireplace filler glows, but somehow never gets burnt up or disintegrated.

What About Lava Rocks for Fire Pits?

Fire pits may actually benefit more from using lava rocks than an indoor fireplace would. In addition to providing aesthetic appeal, the rocks insulate the gas burner from wind, rain, cold and other elements. It also provides a mechanism for the flames to spread apart while giving the entire pit a more evenly spread heat.

Where to Find Fire Pit & Fireplace Lava Rocks

You can buy lava rocks, vermiculite and other accessories for your gas heating fixtures under Emberside’s accessories page.