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Topic Review (Newest First)
02-12-2013 06:11 AM
lochaber Those links seemed to be about sticking rocks into/around fires.

I think boiling is different: the temp doesn't go as high as it would sitting in a fire. The outside of the rock is going to heat/boil before the inside does (probably a miniscule difference unless you are dealing with really big rocks). Also, water trapped in a cavity would be under pressure as it's heated, and this pressure would effectively drive up the boiling temp for the bit of liquid in that cavity. I'm wondering if it's something similar to why boiled eggs don't explode, but microwaved ones will?

Anyways, yeah, don't stick rocks in the oven, or on fires unless you know what you are doing (granite, basalt probably fine, sandstone, shale, slate, limestone - not so much).
and I don't see much point to boiling them anyways, but I don't think there is really any risk to it.

Back to topic, cool find, it does sound like maybe they are excavating or something. Hope some of you Manhattan folk can make some use of it.
02-12-2013 03:12 AM
im2smart4u
Quote:
Originally Posted by lochaber View Post
Have you ever witnessed this, or heard a first hand account of this happening? -I'm rather skeptical that any would actually explode. I could possibly see cracking, but I don't think it would be dangerous at all.

The reason not to put rocks on a camp fire is because of the water present, and there is a tremendous amount of expansion involved when water changes from liquid to vapor form. Rough estimate, I think it's something like a 1000x increase in volume.

As to a gas pocket that's already in the rock, it's probably not even going to expand 2x, since you are only heating it to ~100 celsius
I have had no personal experience, but hear are a few supposed accounts:
http://www.greenscenelandscape.com/W...sMarch2011.htm
http://www.contractortalk.com/f11/la...re-pits-48144/

You are right that it is the moisture, not air, trapped in the rocks. Water expands a lot when converted to steam.
02-12-2013 02:30 AM
philemon716
Quote:
Originally Posted by Trail_Mix View Post
Keep us updated please! This is such a great find!
Rocks are back! The new dumpster is a bit higher, but they filled up half already. What sizes are you specifically looking for? I can pull one or two out (maybe - wife dependent) and hold them for you. They range from 5 inches to large 20 pound pieces.
02-12-2013 12:21 AM
lochaber
Quote:
Originally Posted by im2smart4u View Post
There are some rocks that are dangerous. Rocks like lava rock can have air trapped inside that can explode when boiled. I agree that the warning has been exaggerated, as most rocks are safe to boil, but there are a few that aren't.
Have you ever witnessed this, or heard a first hand account of this happening? -I'm rather skeptical that any would actually explode. I could possibly see cracking, but I don't think it would be dangerous at all.

The reason not to put rocks on a camp fire is because of the water present, and there is a tremendous amount of expansion involved when water changes from liquid to vapor form. Rough estimate, I think it's something like a 1000x increase in volume.

As to a gas pocket that's already in the rock, it's probably not even going to expand 2x, since you are only heating it to ~100 celsius
02-11-2013 09:09 PM
Trail_Mix Keep us updated please! This is such a great find!
02-11-2013 02:10 PM
philemon716
Quote:
Originally Posted by Trail_Mix View Post
Wow, great find, I NEED to hit this up! I hope it's still there tomorrow. Or maybe I'll try and hit it up late tonight. I've got plans till 7:00 though and this is about 45 minutes away from me, and it's probably full of snow still

If anybody is passing by this today and could provide a status update, that would be greatly appreciated!
They towed the dump away this morning as I was walking to work. Looks like they are replacing it with another though.
02-11-2013 07:29 AM
im2smart4u
Quote:
Originally Posted by lochaber View Post
I don't think there is any serious risk of explosion from boiling a rock. At most I can see cracking from thermal expansion.

If I had a good reason to boil a rock, I wouldn't even hesitate, just find a pot big enough, and fill it with water, and fire up the stove.
There are some rocks that are dangerous. Rocks like lava rock can have air trapped inside that can explode when boiled. I agree that the warning has been exaggerated, as most rocks are safe to boil, but there are a few that aren't.
02-11-2013 06:06 AM
lochaber huh, maybe they are excavating inside.

http://en.wikipedia.org/wiki/Manhattan#Geography

Sounds like it might be what you found.
02-11-2013 04:25 AM
philemon716 Still there. Covered in snow...and now a few blue bags of dog poop.
02-10-2013 07:11 PM
Trail_Mix Wow, great find, I NEED to hit this up! I hope it's still there tomorrow. Or maybe I'll try and hit it up late tonight. I've got plans till 7:00 though and this is about 45 minutes away from me, and it's probably full of snow still

If anybody is passing by this today and could provide a status update, that would be greatly appreciated!
02-10-2013 05:47 AM
philemon716
Quote:
Originally Posted by Option View Post
Where is this? Upper westside? I wonder where they (whoever threw them into the dumpster) found these stones from...
Chelsea. They are renovating a historic restaurant / hotel on 23rd street, whose back door is on 22nd street - where the dumpster is found. There are LOTS of it.

Size ranges from small to as large as one man can carry (through the hotel to the back).
02-10-2013 01:38 AM
lochaber The vinegar test can be useful, but a lot of rocks/minerals that will affect hardness won't react to it. If something does fizz, you can be certain it will affect your water chemistry, but no reaction doesn't necessarily mean it's safe/inert.

Quote:
Originally Posted by reddhawkk View Post
philemon716, your rocks look to be granite schist. I am not sure if they will change your ph but they do look good.
I wasn't paying attention to the sparklies, so schist might be more accurate, it's been a while since I've done anything remotely geologic (and I was never good at the mineral ID to begin with...)

Quote:
Originally Posted by MSG View Post
  • BTW, what is the rule to prevent kitchen xplosions when it comes to BOILING??
I'm not sure that boiling is really necessary, I doubt that there is much risk of pathogens. Then again, it might be useful to remove any potential residues that may have accumulated on the rock wherever/whatever it was doing before.

I don't think there is any serious risk of explosion from boiling a rock. At most I can see cracking from thermal expansion.

Best I can figure, this started as a general warning about baking rocks (similar to being careful what you put around a campfire) as some rocks (typically sedimentary) can absorb water, and when heated rapidly, this can convert to steam and fracture the rock violently. I think I seen a lot of similar concerns/warnings over at Dendroboards, so I think it was just an initial precaution that got exaggerated with each retelling.

If I had a good reason to boil a rock, I wouldn't even hesitate, just find a pot big enough, and fill it with water, and fire up the stove.
02-10-2013 12:30 AM
MSG Those stones you found would also make a nice border around a garden if you decide they're not "Aquarium worthy"

Thanks everyone for the guesses.

I do agree with the slate. I've just never seen "multicolored" slate before. I think it was previously used in a tank with cichlids, the rock pictured in the last row I always thought looked like some sort of tree stump. It would be very cool if it does contain IRON or is petrified wood.
  • No one has any idea on the lavender colored stone?

philemon716, you have a good eye. Those stones granite/gneiss have nice rings/layers. Whoever tossed them in the dumpster probably found them laying around in the basement. I think those stones are sometimes mixed in fieldstone foundations.

I think your dog is more scared of you possibly leaving her in the dumpster. That's why she's giving you "freaked out" looks.

I have to go finish shoveling. We easily got 2x the amount of snow you guys received.
  • BTW, what is the rule to prevent kitchen xplosions when it comes to BOILING??
  • I would also give your rocks a good scrubbing with some baking soda & those hand iron type brushes.
02-09-2013 09:39 PM
Option Where is this? Upper westside? I wonder where they (whoever threw them into the dumpster) found these stones from...
02-09-2013 09:36 PM
philemon716 Thank you all. My dog thinks I am crazy b/c I always make her stand by the dumpster (bottom left of image) for a few minutes while I gaze at the hundreds of pounds of rock at my disposal (now covered in nemo snow). This is the second dumpster. The first one was longer and higher and full of rock.

I'll be boiling these for 5-10 minutes and then performing the vinegar test in the next few days.
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