Exploding Rocks!

[heelflip_kid]

Have any of you ever experienced any rocks exploding and/or cracking because of a campfire? The reason it supposedly happens makes sense to me (trapped water and air being heated inside the rock with the heat causing expansion and/or steam and, if there is no release for the pressure, it explodes) but how often does it happen?

I just want to be safe and not worry about shrapnel whilst I'm cooking my bacon

 

[dtownknifekid]

i've been on lots of campingtrips and made boat loads of fire but never have had a rock explode on me. It did however happen to annother troop and one kid did lose an eye but they had not just been using wet rocks but a rock found in some sort of pool of water and i think that is the main reason for it hapening.

 

[Gossman Knives]

You've answered you own question. Don't use river rocks or any rocks exposed to water.
Scott

 

[riddleofsteel]

No but we had a kid put a can of beans right next to the fire. He said he made a hole in it first but later on it blew beans all over several cub scouts, parents and a tent. We looked for the can but never found it.


I have heard of fireplaces built from flat field stones exploding when being first used.

 

[heelflip_kid]

No but we had a kid put a can of beans right next to the fire. He said he made a hole in it first but later on it blew beans all over several cub scouts, parents and a tent. We looked for the can but never found it.

So...rocks that are in rivers/pools/lakes/streams/generally exposed to water are not usable. I would imagine then, that rocks that aren't exposed to that moisture would be acceptable? Thanks for the responses, I guess I did kinda answer my own question

 

[CanDo]

riddleofsteel,

Are you sure that in the case of flat field stones they actually exploded as opposed to just cracking? Maybe if they were very porous and had a lot of air trapped inside...

 

[ejes]

I have heard this story for as long as I can remember, however I have never met anyone that has witnessed it, nor have I seen it for myself. Sounds plausible though.

 

[hlee]

I've heard about it, but never seen it. How many rocks exposed to the elements are NOT exposed to water? Sounds like a future episode of MythBusters is in order.

 

[j williams]

I have had this happen to me a few times. Small thin rocks heating up and shooting out of the fire when they explode. The shoot out at shin level and sting a little when they hit you. I have had this happen nowhere near water as well so I dont know. Just little pebbles, no big rocks though and they never shoot out higher than shin level.......

Feels kinda like being shot by an airsoft rifle...

 

[Ken C.]

I've had rocks crack numerous times. Some pretty big ones, too. but then again we get some BIG fires going. The log stack is at least 3 feet high and then we keep adding to it. It burns all night. The first time a rock cracked it scared the hell out of us and a piece flew off and hit our buddy who was sleeping in the chair right in the face. He was so drunk he didn't wake up.

 

[baldtaco-II]

It happens all too predictably here on this length of beach - http://img91.imageshack.us/img91/9273/drizzldonen1uh8.jpg It's less common with big rocks than with shingle but the principle is the same. It's down the road from my city nest and fires along the seafront are common in the summer. Beach veterans can often be heard warning noobs of the folly of staring gormlessly into the flames and flicking in pebbles. They pop and come hurtling out. I've had a couple of mangy looking bald spots on the head from roasting hot pebbles flying out. It's so predictable that when the vagabonds come down and muscle in for a ponce of your weed and e, you always leave them with a crafty handful in the fire as a goodbye present.

 

[riddleofsteel]

I have always been told that a dry stack fireplace out of flat river rock or fieldstones that are porous must be allowed to dry before using. A mortared fireplace out of rock must be allowed to completely dry before use or you risk rocks blowing out with possible deadly force.

One of the guys that told me that was a stone mason for over 45 years.

 

[OldPhysics]

You've answered you own question. Don't use river rocks or any rocks exposed to water.
Scott

Bingo. I've had it happen a few times ... only when I made a mistake like this.

It's only rocks with a fair amount of water infiltration that experience this issue. It's surely not common.

 

[hollowdweller]

Happened to me many many times

If some sandstone really heats up it will blow. Usually it just cracks.

My favorite story was we were having this huge party at this old strip mine in college.

The party started in the evening but the "advance crew" which consisted of a bunch of us brought the kegs out and got it all put up and tapped the keg and burning fatties.

So we got all drunk and stoned out and were all laying around the fire in our sleeping bags, waiting for the crowd to show up.

Right about that time a big rock blows and my friend Jamie yells "F*cking A!" and holds his sleeping bag up and a "meteor" from the fire burned a silver dollar size hole thru his sleeping bag

Anyway being a strip job the fire was built on rock and all thru the night huge rocks exploded and the assembled crowd would hoot and holler every time one went off just like fireworks It was funny as hell. Nobody else got burnt or hurt other than one sleeping bag

 

[gunknifenut]

I have had a couple crack, but never blow..I never really used any river rocks though. Gene

 

[3wolves]

I have had rocks crack but not explode, one of them (slate?) cracked multiple times and after the fire died down it was in about 20 paper thin slices. When I used to live in Ontario, there was a very bad blizzard once and a couple trees exploded! Turns out it was from the sap freezing and expanding so it cracked the wood. If you froze a wet rock, would it explode?

 

[lambertiana]

This is really only a problem with porous rock, like shale and sandstone. Granitic rocks won't usually do this.

 

[akabu]

Happens many times not just from a stream bed but if there's a heavy rain and the rocks are in a riverlet and get soaked for awhile then its dry when you pick them up
Sand stone and Shale are two bad ones.
Look for stones that are on high ground and not in a depression.

 

[hwtsauer]

I have had it happen. They "pop". Never had one "Explode." But loud enough to wake you up in the night.

 

[sasha]

I had two explode on me.. One of them was a larger rock that seemed solid like a rock should lol.. When it did explode It blow part of the fire so i had to ran around and put everything out...