# Safe (non-exploding) rocks to use for campfire ring? **URL:** \ **Category:** Factual Questions\ **Created:** [October 18, 2002, 4:26pm UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845 "2002-10-18T16:26:03Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![toadspittle](https://avatars.discourse-cdn.com/v4/letter/t/c0e974/32.png) [@toadspittle](https://boards.straightdope.com/u/toadspittle)\ **Post date:** [October 18, 2002, 4:26pm UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/1 "2002-10-18T16:26:03Z")
What sorts of rocks are safe to use around a campfire? Shale was handy for the last ring I built, but I luckily had a nagging suspicion that shale was unsafe to use and never got around to actually building a fire there… So which rocks are OK to use, and won’t explode due to their moisture content? ---
**Author:** ![Mr.Moto](https://avatars.discourse-cdn.com/v4/letter/m/9de0a6/32.png) [@Mr.Moto](https://boards.straightdope.com/u/Mr.Moto)\ **Post date:** [October 19, 2002, 1:34am UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/2 "2002-10-19T01:34:56Z")
Don’t use sandstone. Anything else should be fine. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [October 19, 2002, 1:55am UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/3 "2002-10-19T01:55:47Z")
Volcanic (Lava) Rock?? ---
**Author:** ![lieu](https://avatars.discourse-cdn.com/v4/letter/l/c2a13f/32.png) [@lieu](https://boards.straightdope.com/u/lieu)\ **Post date:** [October 19, 2002, 2:44am UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/4 "2002-10-19T02:44:03Z")
I’ll attempt a search and report back later. However, as a geologist, my first guess would be that any rock type that might harbour air bubbles/sealed pores would be potentially dangerous. Oh yeah, don’t line your pit with oil-bearing liths. Sadelerochit carbs and others are right out. ---
**Author:** ![NotMrKnowItAll](https://avatars.discourse-cdn.com/v4/letter/n/6bbea6/32.png) [@NotMrKnowItAll](https://boards.straightdope.com/u/NotMrKnowItAll)\ **Post date:** [October 19, 2002, 2:44am UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/5 "2002-10-19T02:44:03Z")
My experience is that limestone with chunks of flint in them are no good. Facing flame, they furiously flicks flakes of flint flying. ---
**Author:** ![NotMrKnowItAll](https://avatars.discourse-cdn.com/v4/letter/n/6bbea6/32.png) [@NotMrKnowItAll](https://boards.straightdope.com/u/NotMrKnowItAll)\ **Post date:** [October 19, 2002, 2:51am UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/6 "2002-10-19T02:51:22Z")
My experience is that limestone with chunks of flint in them are no good. Facing flame, they furiously flicks flakes of flint flying. ---
**Author:** ![lieu](https://avatars.discourse-cdn.com/v4/letter/l/c2a13f/32.png) [@lieu](https://boards.straightdope.com/u/lieu)\ **Post date:** [October 19, 2002, 2:56am UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/7 "2002-10-19T02:56:57Z")
I’ll attempt a search and report back later. However, as a geologist, my first guess would be that any rock type that might harbor air bubbles/sealed pores would be potentially dangerous. Permeability isn’t the culprit, porosity and in situ elements are. Oh yeah, don’t line your pit with oil-bearing liths. Sadelerochit carbs and others are right out. ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [October 19, 2002, 3:08am UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/8 "2002-10-19T03:08:45Z")
A double double post split! 😃 ---
**Author:** ![Philosophocles](https://avatars.discourse-cdn.com/v4/letter/p/b38774/32.png) [@Philosophocles](https://boards.straightdope.com/u/Philosophocles)\ **Post date:** [October 19, 2002, 6:10am UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/9 "2002-10-19T06:10:28Z")
Mikey says to avoid pop rocks. (I know…I know, UL) 😃 ---
**Author:** ![DougC](https://avatars.discourse-cdn.com/v4/letter/d/7feea3/32.png) [@DougC](https://boards.straightdope.com/u/DougC)\ **Post date:** [October 19, 2002, 7:40am UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/10 "2002-10-19T07:40:25Z")
- - - Refractory brick? Not quite the natural look and damn heavy to carry around, but they have a rather gothic-type look arranged properly. ~ ---
**Author:** ![Eleusis](https://avatars.discourse-cdn.com/v4/letter/e/f4b2a3/32.png) [@Eleusis](https://boards.straightdope.com/u/Eleusis)\ **Post date:** [October 19, 2002, 8:05am UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/11 "2002-10-19T08:05:00Z")
IANAGeologist but I was always taught that the only rocks to worrry about were the smooth, rounded rocks collected from near bodies of water. Furthermore, I can attest to the fact that I was perhaps 20 years old before I had even heard that warning, and through probably 500 campfires no rock ever exploded or did anything else but sit there and keep the fire from spreading to the nearby underbrush. ---
**Author:** ![voltaire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voltaire/32/313_2.png) [@voltaire](https://boards.straightdope.com/u/voltaire)\ **Post date:** [October 19, 2002, 10:34am UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/12 "2002-10-19T10:34:05Z")
> [@](#): > > \*Originally posted by NotMrKnowItAll \* > \*\*Facing flame, they furiously flicks flakes of flint flying. \*\* Say that fast 5 times! ---
**Author:** ![toadspittle](https://avatars.discourse-cdn.com/v4/letter/t/c0e974/32.png) [@toadspittle](https://boards.straightdope.com/u/toadspittle)\ **Post date:** [October 19, 2002, 11:29am UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/13 "2002-10-19T11:29:01Z")
> [@](#): > > \*Originally posted by DougC \* > \*\*- - - Refractory brick? Not quite the natural look and damn heavy to carry around, but they have a rather gothic-type look arranged properly. > ~ \*\* Yeah-- I might be going with brick for now … reassuring anecdotal evidence, though, eleusis. ---
**Author:** ![Weeks](https://avatars.discourse-cdn.com/v4/letter/w/bbce88/32.png) [@Weeks](https://boards.straightdope.com/u/Weeks)\ **Post date:** [October 19, 2002, 1:57pm UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/14 "2002-10-19T13:57:26Z")
> [@](#): > > Furthermore, I can attest to the fact that I was perhaps 20 years old before I had even heard that warning, and through probably 500 campfires no rock ever exploded or did anything else but sit there and keep the fire from spreading to the nearby underbrush. Amen. 500 other campfires added to your 500 says the only rocks that explode near a campfire are the ones in your mothers worried mind. Sure they might sputter and flake (wet granite) but so what? Thats half the fun of a campfire! Sounds like the “your gonna poke your eye out with that thing” mentality. The real concern here is: What are you going to do now that you forgot to bring matches with you, you knucklehead? Doh! ---
**Author:** ![TV\_time](https://avatars.discourse-cdn.com/v4/letter/t/f17d59/32.png) [@TV\_time](https://boards.straightdope.com/u/TV_time)\ **Post date:** [October 19, 2002, 2:11pm UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/15 "2002-10-19T14:11:37Z")
A pretty good way to avoid exploding rocks is to not collect them from a river or from a stream bed. My experience camping points to those being the ones that explode. I imagine that water has gotten into pockets inside the rocks and the rocks have since become sealed with sediment (or something) and the heat causes the trapped water to vaporize and expand and thus exploding the stones. It doesn’t happen often, but when it does, it is really scary. Isn’t it? TV ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [October 21, 2002, 11:51am UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/16 "2002-10-21T11:51:27Z")
I’ve made a number of fires on river banks, using whatever rocks were handy for the fire ring. I’ve seen quite a few of them crack into two or more pieces (sometimes with a popping sound), but I’ve never seen one explode. ---
**Author:** ![An\_Arky](https://avatars.discourse-cdn.com/v4/letter/a/87869e/32.png) [@An\_Arky](https://boards.straightdope.com/u/An_Arky)\ **Post date:** [October 21, 2002, 12:34pm UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/17 "2002-10-21T12:34:25Z")
Another handy tip would be to make the fire ring larger than the fire. It’s only there to contain the fire in case it gets out of control. An even better idea would be to use an existing fire ring and campsite, so’s not to cause further damage to our treausred natural areas. ---
**Author:** ![China\_Guy](https://avatars.discourse-cdn.com/v4/letter/c/779978/32.png) [@China\_Guy](https://boards.straightdope.com/u/China_Guy)\ **Post date:** [October 21, 2002, 12:50pm UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/18 "2002-10-21T12:50:42Z")
Dunno, I had a few bad experiences in Tibet with shale type. Maybe it was a combination of altitude, temperature and using a mixure of yak dung that you don’t get in low elevations in America. Scary to say the least. Happened a few times over 12,000 feet, and with fairly regular occourance over 15,000 feet. Frankly, I was a little scared to go higher both for my own lungs and for the fire. ---
**Author:** ![lieu](https://avatars.discourse-cdn.com/v4/letter/l/c2a13f/32.png) [@lieu](https://boards.straightdope.com/u/lieu)\ **Post date:** [October 21, 2002, 2:07pm UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/19 "2002-10-21T14:07:20Z")
If heated flint has a liquid dripped onto it, it can send flakes flying. Shale is a source rock for oil and gas and should also be avoided. The shape of a rock, ie rounded, simply indicates a likely transport mechanism and distance. Rounded rocks were probably exposed to water and the more rounded they are, the greater the distance they’ve likely travelled. If you try to stick with unsubmerged, non-organic, non-flint bearing, non-porous rock and don’t put it in direct proximity to the fire, my guess your chance at an undisrupted evening will be greatly enhanced. ---
**Author:** ![einzelwesen](https://avatars.discourse-cdn.com/v4/letter/e/b77776/32.png) [@einzelwesen](https://boards.straightdope.com/u/einzelwesen)\ **Post date:** [October 21, 2002, 2:37pm UTC](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845/20 "2002-10-21T14:37:24Z")
Basically, avoid using all and any igneous (volcanic) rocks. [Next page](https://boards.straightdope.com/t/safe-non-exploding-rocks-to-use-for-campfire-ring/132845.md?page=2)