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Fire Glass Vs. Lava Rock: Which One is Best?

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When planning an outdoor fire pit, you may find yourself wondering which material is better to use.  

Fire glass can produce more heat than lava rock, while lava rock is typically cheaper. Both have aesthetic values, and the choice between the two often comes down to personal preference. 

There are some important differences between fire glass and lava rock. In this article, we will compare the following seven factors to help you decide which of the two best fits your needs and desires:

  • Cost
  • Heat Conduction
  • Aesthetic 
  • Safety
  • Durability
  • Material Combination
  • Additional Uses

Cost Comparison Between Fire Glass and Lava Rock

When choosing between fire glass and lava rock for your next fire pit, there are a few additional cost considerations:

  • Firepit dimensions. The larger the pit, the more costly it will be to fill it. 
  • Ease of access. You may be able to buy one material locally while the other you can only order online. Shipment costs can add up quickly. 
  • Project budget. There are many costs that go into the construction of a fire pit. If this is a new project, especially, you should consider how much of your budget you are willing to allot to materials. 
  • Propane vs natural gas. Choosing which fuel you want is another major cost component to consider. Natural gas is often cheaper but requires the pit to be stationary, whereas propane is portable but requires refilling, which can become expensive depending on use. 

Once you have considered these factors, it’s time to choose your filling material. 

Lava rock is a more traditional material, whereas fire glass is more modern. Therefore, the market for lava rock is much larger, making it a cheaper option overall.

Whichever option you choose, you will want to calculate how much coverage you will need for your fire pit. This will determine how much material you will need to purchase. 

Visit the following link for a free coverage calculator that you can use for both lava rock and fire glass. 

Below we will analyze material-specific cost factors:

Lava Rock

lava rock fire pit

For fire pit use, you will most likely be purchasing lava rock by the bag rather than in mass quantity, such as per ton. 

Lava rock ranges in price, averaging between $7 – $25 per bag. It is important to also pay attention to how many pounds per bag you get. The average bag weight for fire pit use is around 10 lbs. 

Note: lava rock has more volume per pound than fire glass. You will typically need half the amount in pounds of lava rock compared to fire glass to fill your pit. 

Color can affect the price of your lava rock selection. The cheapest lava rock is typically red, which is also the more traditional color for lava rock. 

Black lava rock is the next most common color. While it can be bought for the same price as red rock, it can also be more expensive, depending on the brand. This price difference is largely attributed to the aesthetic value of black rock.

If you are looking to purchase lava rock in mass quantities, expect to pay per ton or per cubic yard.

According to Home Advisor, lava rock costs between $75 – $110 per cubic yard. 

Fire Glass

fire glass

When purchasing fire glass, you will most likely be paying per pound. Depending on the brand, you can purchase fire glass per individual pound, or by larger quantities such as 10 or 20 lbs. 

The reason fire glass is priced this way partially has to do with color. By purchasing individual pounds, you can mix and match different types and colors of fire glass.     

Because there are many varieties of fire glass, prices can vary widely. Most 10 lb. bags average between $25 – $35 per bag. If you are searching for a standard style of fire glass, this means you should look for a product that you can purchase for around $2 – $3 per pound

If you are searching for specific color variations and styles, the price is likely to increase. Depending on what you want, the price can be upwards of $10 or more per pound. 

Finishing on the glass is where you will see the biggest price jumps. For instance, you can buy classic broken fire glass with sharper edges for cheaper or spend more to buy fire glass with finished edges. 

Heat Conduction Comparison of Lava Rock vs. Fire Glass

The material used will affect the amount of heat produced. This, in turn, will affect how much propane or natural gas needs to be used.

Lava Rock

Lava rock does not conduct heat very well. This is due to it being porous and unable to properly absorb or hold heat.

If your fire pit is serving as an outdoor heat source, this could be problematic. It will lead to you having to use much more propane or gas to propel the heat outwards. 

However, if you live in an area with a warmer overall climate, this feature could be more convenient. Lava rock will provide an inexpensive and appealing fire pit filling, without creating too much heat to handle. 

Additionally, lava rock has thermodynamic properties that allow it to work as a mulch-replacement as well. This means your lava rock can serve multiple purposes in your outdoor space, giving you more bang for your buck. 

Fire Glass

Comparatively, fire glass is a much better conductor of heat. The glass absorbs the heat, while the reflectiveness helps to disperse the heat back outwards towards those sitting or standing near it.

The main benefit of this is that fire glass will require much less propane or natural gas. The flame in the fire pit can remain smaller, while still dispersing a good amount of heat.

This makes fire glass a much better option for fire pits in colder climates that are meant primarily as heat sources. 

Fire glass is also able to distribute the heat of the flame more evenly due to there being more and smaller pieces of it compared to lava rock. 

Note: It is possible to achieve a similar effect with lava rock by buying the rock broken up into smaller pieces. However, this may cause additional cost or labor.

Aesthetic Differences Between Lava Rock and Fire Glass

There are many stylistic differences between lava rock and fire glass, as well as many ways to customize each in their own way. 

The most obvious difference is the immediate appearance of the two. Fire glass is reflective and will sparkle under the fire. Lava rock is more rustic and will remain matte despite the firelight. 

Both materials vary in colors and styles that can be purchased. 

Lava Rock

Lava rock does not vary too drastically, but nonetheless, there are a few styles to choose from.

Color

The biggest variation to choose from for lava rocks is color. There are three main colors of lava rock to choose from:

  • Red
  • Brown
  • Black

However, lava rock can also be gray in color, as well. The lava rock below is the traditional red.

lava rock

It is important to note that lava rock in unnatural colors, such as blue or green, may have undergone a dyeing process. Make sure that the lava rock you are purchasing is safe to be used with fire. 

Shape

Lava rocks can also be purchased in different styles. They naturally will have jagged edges, but they can be made into oval shapes with smoother surfaces, also called tumbled lava rock. These types of lava rocks are typically more expensive since more work goes into the production process.  

Fire Glass

Fire glass is highly customizable since glass can come in all shapes, colors, and styles. 

Color

Color-wise, you can find pretty much any color of fire glass you want. There are a few colors that are more commonly used, and therefore less expensive than more rare colors. They include:

  • Variations of blue (teal, turquoise, sky, cobalt, etc.)
  • Black Obsidian
  • Gold
  • White
  • Translucent

Blue is one of the most common colors used because it is the complementary color to the orange tones of the fire. This gives it a visually appealing contrast. The fire glass shown below has several different colors to show from and is highly rated.

glass rock

Style and Shape

There are two main types of styles for fire glass:

  • Broken crystals. These are the pieces without a common shape. They are sometimes referred to as “fractured.” They are jagged in shape with sharp edges.
  • Smooth beads. These are the pieces that do have a uniform, usually oval or circular shape. Their surface and edges are completely smooth. They may also be referred to as drops, rocks, or beads. 

There are, of course, variants to these two styles. The crystal form can have smoothened edges, and the smooth form can be shaped into cubes or other geometric forms. 

Finish

Fire glass can have two finishes:

  • Reflective fire glass will have a mirrored finish on either one or multiple sides that causes the light’s reflection to be much brighter.
  • Non-reflective fire glass will still reflect the light from the fire but in a more uniform and dispersed way.

The pricing of different fire glasses is largely dependent on individual companies.  

Safety Comparison of Lava Rock and Fire Glass

While lava rocks and fire glass are both relatively safe options for fire pits, there are a few serious issues to keep in mind

Lava Rock

The biggest safety concern with lava rocks concerns their porousness. Lava rocks can absorb a lot of moisture from the air and environment they are in. This moisture can then cause the rocks to pop or explode once on fire. 

To prevent this, you need to ensure that your lava rocks are stored in a dry area and are covered from weather and environmental moisture when not in use. 

Running the fire pit on a low heat can also help to dry them out if there is some remaining moisture. However, if they begin to pop at all, turn the fire pit off immediately. 

There is also some misconception that any rocks can be used in fire pits. While lava rocks are safe for fire pit use, here are some similar rocks that are not safe for use in high heat:

  • River rocks
  • Sandstone
  • Gravel
  • Miscellaneous natural rocks

Fire Glass

Like lava rocks, if fire glass is wet, it can cause popping or explosion. Fire glass does not absorb moisture internally the way lava rocks do, however, and is much easier to dry and keep dry.

Fire glass is made from tempered glass that can withstand extreme temperatures without melting or emitting toxic chemicals or gases. 

When choosing a fire glass, it is crucial to ensure that it is properly tempered. Non-tempered glass is highly dangerous under high heat. 

It is important to check reviews of any fire glass product you choose. If reviews report popping, melting, or cracking of any kind, you should consider a different product. 

The style of fire glass you choose is another safety consideration. Crystal forms with jagged edges can look very beautiful and be highly reflective, but the sharp edges do pose a safety threat. 

If you choose a fire glass with sharp edges, the fire pit should be kept out of reach of children or pets when not in use.

Which is More Durable: Lava Rock vs. Fire Glass

Both materials are highly durable, making them great long-term investments for your backyard design. There are a few maintenances to keep in mind, nonetheless.

Lava Rock

Lava rock is a naturally durable material that does not decompose. This makes it highly valuable as a material for fire pits.

The biggest threat to the durability of lava rock is moisture. As aforementioned, lava rocks can absorb a lot of moisture. This, in turn, can cause them to crack, pop, or even explode. 

Drying lava with heat rock should be done with extreme caution and low heat. The company you buy your lava rock from should have instructions on how to properly dry your lava rock.

If your lava rock is left out in the rain for a long period of time, it may be best to just exchange the drenched lava rock for a new set.

It is also recommended that lava rock be replaced every few seasons if heavily used. 

Fire Glass

Like lava rock, fire glass is very durable and does not decompose. There are a few care techniques that fire glass requires that lava rocks do not, however. 

The biggest issue you may run into with fire glass is the material can get fairly dirty. This is caused by residue build-up from the propane or gas, resulting in a discolored film on top of the glass.

Fire glass should be cleaned promptly once you notice residue build-up. The longer it is left unaddressed, the harder it will become to clean. 

Luckily, cleaning fire glass is not an extensive process. All you need is dish soap and water. It is important to rinse the soap off thoroughly to prevent damage to the fire pit. 

After cleaning, the fire glass must be completely dry before going back into the pit. Wet fire glass can pop and explode just like lava rocks. 

Propane is going to dirty your fire glass quicker than natural gas, so pay special attention to this if you choose to use propane. 

Can You Combine Lava Rock and Fire Glass?

After learning about lava rocks and fire glass, you may find yourself still unable to decide between the two. 

The greatest part about these two materials is that they can be combined safely. This opens up new opportunities for new designs for your fire pit. 

Combining the two can have several benefits as well. Lava rock is widely used not only for decoration but for the protection of components of the fire pit. 

This is because lava rock works better as an insulator than fire glass. Therefore, using lava rock as the bottom layer better protects the fire pit from the high temperature.

If you are a fan of the fire glass aesthetic but do not have the budget for an entire pit’s worth of it, using lava rock as a base is also a great way to cut down costs. 

Additional Uses of Fire Glass and Lava Rock

So, you have chosen a material, or combined the two, and are ready to move on to a new backyard project. Lava rock and fire glass could be your inspiration!

Here are a few additional ways to utilize lava rock and fire glass:

Lava Rock

  • Grills. Lava rocks can be a good replacement for charcoal in grills. This can also cut down on gas costs for grilling as well. 
  • Mulch replacement. Using lava rock as a garden bed can be visually impactful, as well as effective. While it is not suitable for all plants, it can help to moderate temperature and moisture.
  • Rock gardens. Lava rocks are a great material to create interesting and intricate rock garden designs.

Fire Glass 

  • Planters. Fire glass is a great addition to bring to your planters. It is especially good at weed prevention, as well as helping to keep the soil from drying out. 
  • Tabletops. Outdoor furniture can be spruced up by adding some fire glass beneath glass or plastic panels to create fun and colorful statement pieces.
  • Walkways or stepping stones. Fire glass can create beautiful details in your walkways, as well as be made into steppingstones. 

Lava rocks and fire glass are both great mediums to use for you fire pits, and to add details around your yard, so have fun and get creative!

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Jena Slocum Co-Founder

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