Can you Have Lava Rock and Fire Glass in the Same Fire Pit?

Disclosure of Material Connection: Some of the links in the post above are "affiliate links." This means if you click on the link and purchase the item, I will receive an affiliate commission. Regardless, I only recommend products or services I use personally and believe will add value to my readers. I am disclosing this in accordance with the Federal Trade Commission's 16 CFR, Part 255: "Guides Concerning the Use of Endorsements and Testimonials in Advertising."

Have you heard of them? Lava rocks and fire glass? They are both elements that can provide unique benefits when added to your gas fire pit—in fact, you need to have at least one. Here, we will cover what each one is, what perks they offer, and what there is to say about putting both in the same fire pit. Can you have lava rock and fire glass in the same fire pit? Check out our advice and need-to-know tips below to find out!

Can you Have Lava Rock and Fire Glass in the Same Fire Pit? Why You Need Either One

When you use a wood fire pit, the wood itself provides an area for the flame and the heat to spread; the more wood you add, the bigger the flame (which is why you should be mindful not to overfeed your fire, by the way). Gas pits, for their part, have only the burner, which will give you a fairly small flame if left alone. Adding a proper layer of lava rock or fire glass provides you with the following benefits:

• Help spread the flame, making it larger and evening it out.
• Hold heat, so you will continue feeling it for a while after the gas pit is turned off.
• Insulate the burner and other components from the worst of the heat, and from any accidental exposure to water, thereby boosting your fire pit’s durability.
• Make your fire pit (and your fire) look better, though this varies depending on which one you pick, lava rock or fire glass.

Lava Rock, or No Rock at All

Spending money on a 6- or 10-pound bag of special rocks sourced from a volcano may seem silly but, in reality, no other rock will do, for reasons that will soon become clear.

When magma flows down the sides of a volcano after an eruption, it immediately begins to cool down. In fact, it can take as little as 15 minutes for a crust to form on the outside, which you could walk over with absolute safety (although it can take far longer for the entire mass to cool off—years, even, if it is thick enough). The rock left behind after lava comes down to ambient temperature and hardens completely, is what we know as lava rock. Given its origins (magma can reach a temperature of over 2000°F at its hottest), lava rock is perfectly capable of enduring the heat generated around your fire pit’s burner. And, due to the flow of gas while its temperature descends, this rock is also porous, which means water passes right through. Ordinary rocks, on the other hand, can turn into a danger if used in a fire pit, or even around a campfire. For starters, they are not as good at enduring high temperatures; and, when heated up, any moisture held within will expand (and rapidly), often causing the stone in question to explode.

To be clear, you don’t need to use lava rock around a campfire; the heat concentration is not as intense as that of a fire pit, and regular stones will be just fine. However, when you collect stones for your fire ring, you should do so as far away as possible from any water source (lakes, streams and so on), so their moisture content will be at a minimum and there won’t be risk of rock shrapnel flying while you’re lounging by the campfire.

Getting to Know Fire Glass

Emphasis on ‘fire’; i.e., it is specifically made for sitting on top of your fire (such as fire pits, but it can also be used on fireplaces). Regular glass, much like the regular sort of stone we were discussing earlier, can explode if brought to such high temperatures—and who wants glass shrapnel flying near their tender face? Fire glass, aside from being tempered for your appliance’s extreme heat, comes tumbled, which means there are no jagged edges to worry about, when handling these colorful chunks. And we say ‘colorful’, we mean it: blue, black, red, white—almost anything you can think of, you can find it.

Types of Fire Glass

Fire glass comes in two main types: reflective, and non reflective. The former comes with a polished side, which can be used to great effect if placed at the top, so the flame will reflect off of it. Non reflective comes with a more dull look, but it is ideal for when you’d like your flame to be the main attraction, without the fire glass distracting from it. Both types offer a decently wide range of colors, so it should be easy enough to find the hue you want regardless of the texture of the glass itself.

Can You Have Both?

Now that we know what lava rock and fire glass are about, we get to the big question: can they be mixed in? The answer is a resounding yes. Some sources suggest a 1:1 proportion, that is, equal parts lava rocks and fire glass; some others would have you do most of the filling with lava rock. Layout suggestions vary as well: you can either create an actual mix (intermingling the glass and the rock), or place the lava rock at the bottom, and the fire glass on top.

The choice is always yours; that said, we feel that using more lava rock than fire glass (as opposed to 1:1) and layering the glass on top rather than mixing it all in, is the best way to do it. We see three benefits in doing it this way: first, you get the best of both—the superior insulating properties of lava rock, and the enhanced looks of fire glass. Second, it simplifies maintenance; lava rocks and glass fire involve different methods for cleaning, and if you mix them in you’ll have a harder time separating them. And third, it’s more economical, as fire glass is more expensive than lava rock, and this method minimizes the investment.

If You Only Want One

To reiterate: using both lava rock and fire glass nets you the main benefits of both, especially when distributed appropriately within your fire pit. That said, there’s nothing wrong with wanting to choose only one. Those who are thinking along these lines might be wondering which one is better, and we are happy to provide some guidance on the matter.

1. Lava Rock

If providing appropriate insulation and flame distribution is all you care about, then lava rock is all you need: it is, as mentioned, better at insulating than fire glass is, and it is also fairly cheap compared to fire glass, as it’s not that hard to source. Maintenance is simple enough, too, as you can simply dump your rocks into a bucket of water, let them soak a bit, and that will get rid of just about any little bits that might be sitting within the pores (which can, down the line, affect drainage). Just remember to let them dry out completely before using them again, so there won’t be any risk of explosion.

Two are the main drawbacks of lava rock. One, which might fairly obvious, is its looks—while they should be quite suitable for any fan of a natural aesthetic, they are likely to be too drab for some tastes. Furthermore, you can only expect to find them in black, or in red if you look hard enough. The other shortcoming is durability: lava rock lasts only about 4 years, only a fraction of fire glass’ longevity.

2. Fire Glass

Anyone who cares about looks is likely to be better served by going the way of fire glass. It may not be forged in the depths of a volcano, but it is still perfectly capable of enduring your fire pit’s heat. Aside from reflectivity, you get to pick the color that better complements your appliance and surrounding space. And there is no need to worry about cuts, as every chunk comes tumbled for your convenience. It’s better at holding heat, which means you can expect at least one hour of warmth after your fire is out, whereas lava rock will only go on for about 45 minutes. And this glass will also last longer, about 20 years give or take, as long as it is handled properly (it’s still glass, so it is somewhat fragile).

Fire glass, it has to be said, is not perfect. To begin with, it can darken if used in tandem with propane. This is not a sign of deterioration, merely soot resulting from gas burning poorly; and it can be mitigated easily enough—by using natural gas, using a darker hue of glass, or installing an air mixer for a more efficient burn. Cleaning fire glass is almost as simple as it is with lava rock, except you need additional elements (vinegar, a dedicated strainer, among others); fortunately, this will also clear the soot. And, since it is man made, it is significantly more expensive than naturally sourced lava rock.

Can you Have Lava Rock and Fire Glass in the Same Fire Pit? Summary

Mixing lava rock and fire glass is not only possible—it is a sound idea, as long as it is done right. It will be more economical, functional, and aesthetically pleasing. That said, if you for any reason prefer to use only one of them, it is perfectly possible. Your choice will depend on your budget, looks preference, and willingness (or lack thereof) to perform the appropriate maintenance.