A Complete Guide To Choosing The Best Rocks For Sauna

Most sauna users agree that the heater is at the heart of their sauna. And as a sauna enthusiast and expert, I second this. 

But what if I told you that sauna rocks are equally important. So much so that go for the wrong rock type and you’ve got a ruined experience and a disaster brewing, making it just as important as sauna insulation. 

That’s because the type, size, quality, and placement of sauna rocks can completely change the way your sauna performs. This includes everything from heat retention and steam quality (löyly) to safety and longevity.

Now, I am sure you’d be wondering already about what are the best rocks for sauna and how do you use them for an optimal sauna experience. 

Read on as I walk you through all the sauna rock types out there along with my own experience, research, and insights. 

Why are sauna rocks so important to begin with?

​I am often asked by my clients why sauna rocks are so important and whether or not they could do without these stones. 

So, before I list the best sauna stones out there, let me first tell you why these rocks are essential to your sauna. 

For starters, picking the wrong sauna stones can do more than just ruin your experience, it can pose a real safety hazard. After all, these rocks aren’t not for aesthetics and they drive your sauna's overall performance. 

For instance, sauna stones are responsible for evenly transferring heat from your heater to the room and storing that heat for longer sessions. 

Also, they create löyly or the hot steam that forms when you throw water on hot sauna stones. And depending on your rock type, this can either be soft or sharp.

Meaning even with the best sauna heaters, chances are you could end up with a not so pleasant heat if the stones for sauna aren’t optimal. 

Worse, if you go for the wrong stones, they might even crack or explode. 

What are the best rocks for sauna?

Now that you know why stones for sauna are so curial, let’s have a look at what are the best options out there and what makes them excellent. 

You see, the best sauna stones are those that don’t crack or explode under intense heat and create a soothing flow of steam. 

And to that end, here are a few rocks that fit in perfectly: 
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1. Peridotite

Peridotite is a dense magnesium and iron-rich volcanic rock that’s ideal for sauna use. 

Why? 

First, it holds heat extremely well and can withstand repeated water applications without cracking, thanks to its structure. 

In fact, saunas in Finland have traditionally used this rock for thousands of years because it produces smooth and full-bodied steam. 

Not to mention peridotite has one of the highest thermal shock resistances among sauna-approved rocks. Meaning it can handle hundreds of heating and cooling cycles without breaking down and last you for years even with intense use. 

So, if you want the closest thing to the authentic sauna experience you’d find in Finland, this is the rock to use.
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2. Olivine diabase (also called Olivine basalt)

​Olivine diabase, also known as olivine basalt, is among the best rocks for sauna because of its incredibly even heat distribution and excellent durability. 

This is a crystalline volcanic rock that can store large amounts of heat and release it slowly. As a result, it produces thick rolling steam when you pour water over it. 

These rocks have one of the longest life spans and need  minimal maintenance. And while they’re more expensive than basic options, their performance and longevity make them a worthwhile investment. 

Simply put, if you’re someone who frequents the sauna regularly and wants a consistent professional-grade experience, Olivine diabase is perfect for your needs.

Bonus:
Apart from home saunas, you’ll also find Olivine diabase rocks in commercial sauna heaters like the HUMM HIVE 18 due to their robustness.
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3. Vulcanite or volcanic stones for sauna

Vulcanite is a lighter volcanic stone that heats up quickly and is often used in smaller or portable sauna units. 

And although it doesn't retain heat for as long as denser rocks like peridotite do, it’s still got a fast heat-up time. So, if you’re looking for a quick and short sauna session, this is apt for you. 

The best part: For those of you who are short on space or using a mobile electric heater, vulcanite might be the most practical option, thanks to their light weight. . 

In fact, this is also why vulcanite rocks are ideal for outdoor setups like DIY sauna tents or barrel saunas. 

Note:  
If you reheat these rocks more often, their lightness might affect steam quality in the long run. 
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4. Gabbro

This coarse-grained igneous rock has moderate heat retention and durability. And while not the top performer in terms of thermal shock resistance or steam quality, it still offers a decent sauna experience for its price. 

Gabro is Often found in entry-level saunas. And it is suitable for you if you’re an occasional user or a budget-conscious buyer

However, you should be aware that it’s more prone to cracking over time compared to higher-end rocks. So, I don’t recommend it for long-term or frequent use.

That said, if you're just getting started with saunas or experimenting with DIY builds, Gabro is a decent stepping stone.

What is the worst rock for sauna?

Having seen the best rocks for sauna, let me now tell you about the worst rock you can possibly use in a sauna. 

And no, it’s not Limestone or Quartzite or Marble. 

I am talking about Granite, which despite being visually appealing, is one of the worst choices for sauna rocks.

But why is it a bad choice? 

To begin with, it’s porous and prone to cracking under sudden temperature changes. 

Also, it often has moisture trapped inside and when exposed to high heat and water, it can shatter violently. This poses a serious risk to both people and equipment in the sauna. 

So, despite its popularity in home décor, granite just doesn’t belong in a sauna. And this is also why many sauna equipment manufacturers explicitly advise against it.
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Which stone types should you avoid for sauna?

When it comes to sourcing stones for sauna, you might feel tempted to collect rocks from your backyard or a nearby riverbed. But let me tell you that this is risky unless you understand geology.

How? 

As I said earlier, rocks that contain moisture (like river rocks) or have internal cracks can explode under heat. 

For instance, stones like Sandstone or Limestone crumble quickly. This also goes for Soapstone, which, although thermally stable, is too soft and breaks down easily. 

Overall, here are a few stone types I suggest you avoid: 

• River rocks (contain moisture, can explode)
• Sandstone, limestone, soapstone (soft and crumbly)
• Quartz (can crack violently and dangerously)
• Any rock with visible veins or cracks

A good rule of thumb? 

Avoid any stone that looks cracked, veiny, or crumbly. 

To do so, you can tap it against another rock. And if it makes a dull thud, it’s too porous.
A clear hard clink, at the same time, means it’s dense and likely safe.
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Can you source stones for sauna from nature?

Yes, but you have to be meticulous. 

You see, a lot of sauna enthusiasts swear by locally sourced rocks, especially from volcanic or glacial regions in the northern states of Montana, Washington, Oregon, and Wyoming. 

But if you want to do so, I suggest you select stones that are dry, dense, and crack-free. 

Also, you should stay away from river beds as they usually contain water-logged stones. You can instead head inland and look for smooth and heavy rocks. 

Now, before you use these DIY sauna rocks, test each one of them with a hammer. If it fractures or crumbles, it’s no good. 

Next up, bake the rocks in an oven for several hours at gradually increasing temperatures to expel any remaining moisture. Only use rocks that pass every test. It’s extra work, but it can yield excellent, personalized results.
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Big vs. small sauna rocks: What’s better?

The size of your sauna rocks can offer the sauna’s heat-up time, steam quality, and airflow. 
For instance, large stones (4–6") retain heat the longest and require fewer replacements, but they take a while to heat up. 

Similarly, small stones (1–2") heat up fast and produce rapid steam, but they cool quickly and can clog air circulation if overused. 

Here’s a quick comparison:​

Rock Size	Pros	Cons
Large (4–6")	Retains heat longer, fewer rocks to clean	Heats up slowly
Medium (2–4")	Best heat-to-steam balance	None really
Small (1–2")	Quick heat-up, good steam	Cool down fast, clog heaters

So, what’s the best strategy, you might wonder? 

I suggest you use a layered approach whereby you’d place large stones at the bottom for long-term heat, then medium and small stones on top for responsive steam. This will maximize airflow, heat retention, and steam performance.
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How many sauna rocks should you use?

Talking about the total number of sauna rocks, a general guideline is to use 1–1.5 pounds of stone per kilowatt of heater power. 

For instance, a 6 KW sauna heater should have around 6–9 pounds of rock. 

But that’s just a baseline and you should check your heater's manual for exact capacity. Most electric heaters have rock cages that hold 30–50 pounds of stone, so ever exceed that.
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How to arrange stones in your sauna?

The way you stack your sauna rocks can drastically affect airflow and performance. You want the rocks to be loosely placed and not crammed or wedged in. 

Here, you can stack larger rocks at the bottom and medium or smaller ones on top. This ensures better heat transfer and quicker steam production. 

​Note: Avoid letting stones rest directly on heating elements unless your heater’s design allows for it.
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What’s the best way of pouring water on sauna rocks?

I am often asked what’s the best way to pour water on sauna rocks. So, here are a few best practices as per sauna etiquette and safety guidelines that you can follow:

• Stick to water only (99% of the time).
• Add a few drops of essential oils or sauna oils for rocks in a ladle, and not on the rocks directly.
• Citrus, eucalyptus, or pine are good choices.
• Never pour sugary, oily, or soapy liquids as these can gunk up your rocks and ruin your heater.

Final words

By now, I am sure you know how to source the best rocks for sauna and do so like a pro. 

You see, when you fire up your heater, the sauna rocks get searingly hot. And then you douse them with water, instantly cooling them by hundreds of degrees

The stones need to survive these intense thermal cycles and do so for years. And to that end, they need high density to hold heat effectively, low porosity to resist moisture absorption, and strong thermal shock resistance to avoid shattering.

However, this sudden shock is brutal on poor-quality stones and can lead to uneven heat, poor steam production, or even explosive cracking in worst cases.

This is exactly why I always suggest you go for nothing short of the best sauna stones. After all, it’s better to spend a few hundred dollars extra than have a safety hazard in the making. 

Got more questions or need help with installing a sauna in your home? 

You can get in touch with us!

At Steam & Sauna Experts, we are seasoned sauna installation experts with a decade long expertise installing top-of-the-line saunas across South Florida and beyond. Also, our online storefront features industry-leading sauna equipment and accessories with a free 2nd day delivery. 

In short, we’ve got all your home sauna needs covered on budget.
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Frequently asked questions about stones for sauna

Can I use lava rocks in my sauna?

Yes, you can use lava rocks in your sauna. 

But you need to be very selective about the type and go only for sauna-appropriate volcanic rocks like peridotite or basalt.

These stones are dense, thermally stable, and resistant to thermal shock, making them safe and effective for regular sauna use. 

Also, avoid the porous lava rocks commonly sold for BBQ grills or landscaping since they’re often filled with air pockets and moisture, which can cause them to crack or crumble.

Always ensure your lava rocks are dense, dry, and intended for high-heat applications, preferably sourced from reputable sauna suppliers.
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Why did my sauna rocks explode?

If your sauna rocks exploded, the most likely culprit is that they were either too porous or contained moisture. 

So, when a rock with internal water is rapidly heated, the water turns into steam and causes the rock to fracture or even explode. 

Also, porous rocks can also trap moisture deep inside, even if they seem dry on the outside.

Another issue might be pre-existing cracks or veins in the rock which act as stress points and weaken the rock under thermal pressure. 

I suggest you test rocks by tapping them together. Look for a solid, clinking sound as it indicates density. A dull thud, at the same time, means it’s porous or cracked. 

If you're collecting rocks from nature, make sure to bake them slowly in an oven (starting around 200°F and increasing gradually to 400°F) to remove internal moisture.
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Do sauna rocks make a difference in an electric sauna?

Absolutely!

Sauna rocks are crucial in an electric sauna. These rocks don’t just sit there for looks; they store and distribute heat, control steam production, and protect your heating elements from overheating.

If you choose the wrong rocks, they can disrupt airflow, overwork the heater, and reduce the overall efficiency of your unit. 

In some cases, improper rocks can even shorten the life of your electric heater. 

Good-quality stones provide consistent, radiant heat and allow you to pour water safely for löyly. They also reduce the risk of localized overheating by creating a balanced thermal mass around the heater.​

Should I clean sauna rocks?

Yes, you should clean sauna rocks periodically. And you can do so by following my guide on how to clean a sauna.  

Over time, sauna rocks can accumulate soot, ash, scale, and mineral deposits, especially if your water contains minerals or if you use essential oils frequently. 

Dirty rocks don’t transfer heat as effectively and can develop off-putting odors when hot. 
So, every 3–6 months, remove the stones and rinse them with clean warm water. Let them dry completely before returning them to the heater. 

Also, inspect each stone for cracks, crumbling edges, or signs of white residue (a sign of mineral buildup or ash) while cleaning. And replace any damaged or overly worn stones.
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When to replace sauna rocks?

Even the toughest sauna rocks degrade over time. Cracking, crumbling, and white ash buildup are all signs your rocks are wearing out. 

If your sauna isn’t producing as much steam or smells weird during use, your rocks may be compromised. 

​Inspect them every 6–12 months, especially if you sauna multiple times a week and if you think they’re compromised, replace them.