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HB2

Braidwood Iron Concretions

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HB2

I am new to the fossil collecting hobby and am attempting to open my iron concretions collected in Braidwood, IL using the freeze thaw method.  I am doing it in my freezer in a single layer in a plastic shoe box.   When they are thawing at room temperature the outer layers are crumbling.  The nodes have not split yet.  Is that normal or am I doing something wrong?  Thanks.

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Tidgy's Dad

Hello, and a very warm welcome to TFF from Morocco! :)

I think that happens sometimes. 

I know someone who does freeze thaw on Mazon Creek concretions who'll know more.

@Nimravis

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HB2

Thank you for your prompt response.  I worry about ruining the integrity of the fossil.  Any and all advice is much appreciated! :)

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ynot

Welcome to TFF!

As I understand it, yes it is normal for them to shed layers.

 

If You search the forum for "freeze thaw" You will find several threads that discuss it.

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HB2

Thank you, I'll check it out!

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KimTexan

This post may be helpful to you.

 

 

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Nimravis
On 6/2/2018 at 7:02 PM, HB2 said:

I am new to the fossil collecting hobby and am attempting to open my iron concretions collected in Braidwood, IL using the freeze thaw method.  I am doing it in my freezer in a single layer in a plastic shoe box.   When they are thawing at room temperature the outer layers are crumbling.  The nodes have not split yet.  Is that normal or am I doing something wrong?  Thanks.

Like others @ynot stated, that is common when freezing them, keep at it and see if anything pops open, they could contain something and they may not. It has been a general consensus that there had to be some type of nucleus that the sediment formed around to make the concretion, but many times nothing reveals itself. If you have a chance take a look at my thread in the “General Discussion” section titled “Sometimes You Have To Whack It”. On a daily basis I post fossils that I have found in concretions from Pit 11 or Pit 4 that I opened that day by hitting them with a hammer. I am not telling you to do that, keep trying your freeze / thaw method and good luck.

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Rob Russell

I agree with Nimravas.  After ten or twelve attempts I usually tap around the edges of the concretion with a small hammer to see if I can persuade it some. If you hear a deep hollow thud when you tap it, it should open. If it’s a high pitched solid ping, it’s not ready.  Lol.  I’ve battled many stubborn concretions that peeled and flaked badly during the freeze/thaw cycles, and still wound up producing nice shrimp and worms.  It’s a tedious, yet rewarding, process. 

Good luck! And show us your results!  

Rob

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HB2

Thanks everyone!!!  I'll check out the article.

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digit

Often, there are concentric shells of thinner material surrounding the core siderite nodule. It is quite common to have these layers peel off during the freeze/thaw process. Kinda like peeling hardboiled eggs sometimes. I usually tend to reserve one shelf in my freezer for a plastic shoebox full of nodules. I store the remainder of my stash in a 5-gallon bucket filled with water. The trick to the freeze/thaw process is to get water to saturate into the nodule and then the expansion of the freezing water is what helps pop open the nodule.

 

When I've timed a trip properly to make it up to Chicago during Mazon Creek nodule hunting season, I usually bring back a pretty sizeable stash. I soak these for a week or so in the bucket in my garage and scoop out a couple of handfuls to take to the freezer. I let them freeze for a couple of days and then thaw them out in some warm water. After peeling off any shells and tapping any that seem likely to pop, I take those that haven't split and dump them into my "out" bucket (also filled with water). It takes me a couple of weeks to work my entire stash from the "in" bucket--through the freezer--and into the "out bucket". Once they've all made a round through the freeze/thaw cycle. The "out" bucket becomes my new "in" bucket and I repeat the process (over and over again).... This gives the nodules plenty of time to be soaking between freeze cycles. There is no need to keep them in the freezer for an extended time period as any weakening of the nodule will happen as the saturated water freezes in the nodules. Once it is frozen there is no additional mechanical work that the frozen water will do so extra days in the freezer only add to the cycle time but do nothing more toward getting the nodules open.

 

Sometimes light taps with a small hammer will help the nodules to shed those pesky external layers but try to resist the urge to smack them with a sledge. If you do, you'll run the risk of damaging what could be a cool fossil.

 

 

Post some photos when you get some nice nodules to reveal their fossils.

 

 

Cheers.

 

-Ken

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HB2

That's all great information, thanks Ken!  It sounds like I'm on the right track.  I'll keep at it!

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caldigger

As I told HB2, I attempted to cycle some nodules I got from Rob R. a few years back. At that time I didn't know the proper method and apparently did not soak them long enough each cycle ( only about an hour...if that!).

The nodules kept peeling / flaking off until they became so thin there wasn't enough of a core to get anything from.

I will just let them soak away the next time I give this a try.

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Wrangellian

When I tried cycling a similar load of Mazons a while back, I let them soak for at least a day, if not 2 or 3, and many of them still flaked away until there was just an angular core left. Did I still not soak them long enough? None of them turned out to have anything to speak of in them, so maybe that was the problem - would they have split more readily if they contained anything?

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digit

In my limited nodule experience, the nodules with nothing in them either split very early on or peeled away to nothing. It seems that the nodules with something in it are always the most difficult to get to pop.

 

 

Cheers.

 

-Ken

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HB2

I had approximately a dozen that I was working on.  They varied in size.  Most of them crumbled away to almost nothing.  I "encouraged" one of the larger ones to open.  There wasn't anything in any of them.  Fingers crossed for the next round.

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