Fire Glass vs Lava Rock for Heat, Looks, Price, and Durability

Researched & Written by Craig

There’s nothing like a blazing fire pit to bring family and friends together on a chilly night.

If you’ve just bought a fire pit or you’re reviving one in your back yard, you might be confused about which topping to buy.

Should you get fire glass or lava rock? How are they different? Can they be used together?

In this article, we give you the lowdown on what these mediums are, how they compare, and which to choose for your fire pit.

Are you ready to make your fire pit the blazing hearth of your home? If so, read on!

What is fire glass?

Made with tempered glass fragments, fire glass is a heat-resistant medium used in fireplaces or firepits to cover the jets, reflect light, and disperse heat.

Tumbled and polished to remove the sharp edges, it’s available in hundreds of different colors and comes in reflective, semi-reflective, and non-reflective finishes.

shattered glass
Glass can be the perfect topper for your Fire Pit

Fire glass doesn’t melt, burn or shatter, nor does it emit toxins or smoke when burned – unlike other mediums like wood. In fact, fire glass can emit up to four times more heat than wood, making it a cleaner and more fuel-efficient heating option.

shattered glass
Glass is eco-friendly and can give you more heat than wood

What is lava rock?

As the name suggests, lava rock comes from deep inside the earth’s crust. When a volcanic eruption occurs, the molten rock cools and turns into a porous, igneous rock known as basalt – or lava rock.

In the US, lava rock is mined from ancient volcanoes in Utah, California, and New Mexico – which means that this rock can be up to 2,000 years old. Lava rock is usually black, brown or red and covered in small holes, much like a hardened sponge. This is due to gases that escaped during the cooling process.

Like fire glass, lava rock is tumbled and comes in different shapes and sizes. In addition, its volcanic origin means that it can withstand high temperatures without emitting smoke or toxins, making it suitable as a topping for gas or propane fire pits.

lava rocks
Like glass, Lava Rock is also eco-friendly

Which is better: fire glass or lava rock?

The purpose of fire pit toppings is to protect the fuel jets, disperse flames, and radiate heat. But how do fire glass and lava rock compare? Does one medium stand head and shoulders above the rest? Let’s find out!

Heat

When it comes to heat conductivity, fire glass can retain heat for longer.

That’s because it has reflective surfaces that both absorb and reflect heat. What’s more, you don’t have to use as much gas or propane to reach or maintain the temperature you want. The glass does all the work for you!

Lava rock, on the other hand, is a poorer conductor due to its porosity. That doesn’t mean it can’t conduct or retain heat; it just doesn’t do it as effectively as fire glass. As a result, you get less heat. This may be fine for small spaces or mild winters, but it might not cut the mustard in frostier climates.

To counteract this, buy smaller lava rocks. They cost more but they improve heat retention and radiate more warmth. Or consider combining them with fire glass.

Looks

There’s no doubt that fire glass provides a dramatic backdrop to your fire – particularly at night. The glass fragments glitter and sparkle, bringing atmosphere and light to our outdoor spaces. Because they’re small and evenly sized, the flame literally dances over them, giving you a dazzling light show.

The endless range of colors and shapes also means that you can find something to suit your tastes and décor – and it can last for years if you look after it. If you use propane, though, it might leave a dirty residue on the fire glass. If that’s the case, clean the glass regularly to keep it looking fresh and translucent.

If you prefer more organic mediums, lava rock will give you the natural look you desire. It won’t deteriorate or stain, and it’ll give you a controlled and even distribution of flames.

Unlike fire glass, lava rock is only available in black, brown, and red. This is because it’s all-natural – no dyes or powders have been added! If you’re after a natural look that harmonises with your garden, lava rock will blend in seamlessly.

Lava Rock on fire
All Natural Lava Rock blends seamlessly

Durability

Fire glass is extremely durable. It can last up to 20 years if properly maintained. All you have to do is toss it every year (to expose fresh glass) and clean it when it starts to look dusty or dirty. This is best done with soapy water or one-part white vinegar to one part water. Make sure you let the pieces dry out thoroughly before you put them back on the fire pit 

While fire and heat won’t alter the color of fire glass, sunlight can fade it, particularly if the glass is dark-colored. To prevent this from happening, use a stainless-steel cover during summer.

The lifespan and maintenance of lava rocks are similar to fire glass. To prolong their life, wash them regularly with water and let them dry naturally. If the pit is not in use or you experience hot summers, use a cover to prevent fading.

If you’re done with your lava rocks and you’re not sure what do with them, you can always use them as much for your garden. While they don’t add nutrients to the soil, they can assist with water flow, suppress weeds, and keep your soil warm in winter.

Safety

Fire glass and lava rock are safe for both inside and outside use. That’s because they don’t produce smoke and remain stable at high temperatures. However, there is one risk factor that applies to both. If either medium is exposed to water, it can pop and explode when you fire up the burners.

This can be avoided by making sure that the glass and rocks are moisture-free. If you’ve had rain or the medium has been recently washed, leave it out in the sun until it’s completely dry. Better yet, protect it with a stainless-steel cover when the pit is not in use.

One thing to remember is that new lava rocks can sometimes harbor moisture, so start them a low heat to dry them out. When you do this, keep away from the pit for about 30 minutes in case there’s any popping. Once the popping has stopped, you can approach the fire pit and enjoy the warmth.

Price

Fire glass is small and heavy, which means you need several pounds to fill a fire pit. This can make it 3–4 times more expensive than lava rock. If you choose finished edges or unusual colors, the cost can increase further. Having said that, fire glass doesn’t need as much gas or propane to radiate heat, which means you could save money in the long run.

Lava rocks are bigger, lighter, and less expensive than fire glass, which means you’ll need half as many to fill the same pit. Red is the cheapest option because it’s more readily available, but black is not far behind.

Costs can increase depending on the size and shape. What’s more, lava rocks need more fuel to achieve the same level of heat as fire glass. Does this make a difference in the end? Not really. Pound per pound, lava rock is still more cost-effective than fire glass.

Can you mix fire glass and lava rock in a fire pit?

If you want the best of both worlds, you can combine fire glass and lava rock in the same pit. Not only will it save you money, but it’ll also give your fire a distinctive look.

When using both, lava rock should be placed at the bottom because it’s a better insulator than fire glass. This means it’ll protect the jets and prevent the base from getting too hot. The fire glass layer should then be placed on the top. A 50/50 ratio should work, but you can vary this according to your preferences.

Some suppliers sell pre-mixed blends of fire glass and lava rock, but this doesn’t allow for the energy-efficient layering described above. If in doubt, consult your fire pit manual about the recommended ratio for your model.

The final verdict

Both fire glass and lava stone provide an attractive and robust topping for your fire pit.

If you want warmth, sparkle, and a contemporary look for your fire pit, fire glass is a great choice. While it’s slightly more expensive than lava stone, it’s a great conductor of heat, which means it’ll save you money on running costs, particularly if you use natural gas.

Lava rock is ideal if you want a gentle warmth that takes the chill out of the air. Its organic look is suited to gardens that embrace natural forms and textures, and it’s affordable if you’re on a tight budget.

Apart from heat level and price, there are few other differences between fire glass and lava stone. Both are safe, heat-resistant, and durable – as long as they’re kept dry and protected from the elements.

In the end, it boils down to personal taste. Do you prefer modern elegance or rustic charm? Bright reflections or matte restraint? Either way, you’ll have a stylish and protective topping for your fire pit.

If you’re undecided, you can always mix fire glass and lava rocks together. Not only will this reduce costs (particularly if you’re leaning towards glass), but it’ll provide great heat efficiency and visual impact.

Thank you for reading! I hope you’re one step closer to buying the right medium for your fire pit. Want to read more comparisons? See our related articles below.