Splitting Green River Fm Split Fish Layer

[Ivar]

Starting to prepare specimens from Green River Fm Split Fish Layer.  Several are quite thick - up to 2-inches.  I would like to split them further but the pieces seem a lot harder than when collected. Presuming this is because they are much dryer (collected in early June, rock still very moist).  Questions:

1) Is the dryer rock likely to split less cleanly than it did when moist?

2) Will re-hydrating* the rock make them easier to split cleanly?

3) Even if it does, is re-hydration likely to loosen the fossil on the upper surface of the rock?

 

I could just experiment but would hate to loose a good specimen in the process.  Thanks for any help.

 

 

*I could re-hydrate by submerging in water but that seems most likely to damage the fossil.  The first approach I would try is to support the slab over water in a closed plastic containers.  Placed in the sun, the high humidity should re-hydrate the rock fairly quickly. Any other re-hydration ideas are most welcome.

 

 

[Randyw]

@Ptychodus04 @RJB are a couple of our fish experts I’ll tag them in. You should get an answer fairly quickly. I’ve split some thinner slabs that I’ve gotten from members here but nowhere near enough for me to offer meaningful advice. If your specimen is fairly close to the surface I would not soak the whole piece though. I do use some water while prepping them though...

[grandpa]

First:  Hello Ivar and welcome to TFF from Austin, Tx.  You are in the right place to find answers to such questions

Second:  I have no direct experience with GR fm. fish.

But third:  It would seem to me that the experts on the answers to these questions would be the folk in WY who own the fossil fish quarries in the GR formation.  They might even be able to supply different answers for each of the various layers of deposition.  Have you considered contacting them?

[Ptychodus04]

I would not recommend soaking the slabs as it will make the rock more likely to crumble. I would start a split by using a thin, wide putty knife as a chisel. This is your best chance to get a good break. Keep in mind that any splitting comes with the opportunity to ruin the fish you can see. 

[Ivar]

11 hours ago, grandpa said:

First:  Hello Ivar and welcome to TFF from Austin, Tx.  You are in the right place to find answers to such questions

Second:  I have no direct experience with GR fm. fish.

But third:  It would seem to me that the experts on the answers to these questions would be the folk in WY who own the fossil fish quarries in the GR formation.  They might even be able to supply different answers for each of the various layers of deposition.  Have you considered contacting them?

I emailed the quarry but have not heard back.

[Ivar]

11 hours ago, Ptychodus04 said:

I would not recommend soaking the slabs as it will make the rock more likely to crumble.

Kris, the rock is sufficiently indurated that I don't think it will crumble. I am very concerned that soaking would release the specimen that is directly on the slab surface. However, your comment makes me realize that I can run at test.  I will cut a piece of the end of a larger slab, soak it, and see what happens.

[Randyw]

I’m with kris on this. Especially if the speciman is on the surface. I think between kris and rjb they have prepped close to 20,000 grf fish....

[caldigger]

5 hours ago, Ivar said:

I emailed the quarry but have not heard back.

Maybe closed down for Covid and if no tours being offered, probably no point in checking emails every day. 

[Ivar]

7 hours ago, Ivar said:

Kris, the rock is sufficiently indurated that I don't think it will crumble.

Well, you were right.  I didn't want to cut any thicker pieces because they were pretty close to display size already but I tried a couple  of thinner pieces.  The wet rock is clearly weaker and could crumble.  Still, I was able  to cleave about 1/8" off the back of the 3/8" piece.  The thinner one came off in pieces but the thicker stayed whole. But that could have been luck.

[Ivar]

1 minute ago, Ivar said:

But that could have been luck.

Kris, rjb and others, perhaps there is a way to minimize relying on luck.  A couple days ago I put thinned white glue solution (maybe 4 water : 1 glue) onto a thin piece to see how it looked. The piece yellowed but there seemed no other discernible evidence it was there. The yellow went completely through the about 3/16" piece.  I soaked it today and the glued part does not show any tackiness or other ill effect. That could help hold my piece together during splitting - unless it soaks in past where I want to split.  I plan to try some PVA to preserve the specimen. Will it yellow like the white glue? Since the solvent is acetone, will it tend to soak in deeper?  

 

Thanks for helping out a newbie.

 

Ivar

[Ptychodus04]

It will still yellow the matrix a bit. That’s just the nature of the split fish layer. Even doing this, you still have to rely on luck as the layers often don’t split where you want them to.

 

one possibility is to cut a groove around the slab where you want to split it to help encourage it to break there. A diamond grinder wheel will make short work of it. You can also use a hand saw if you don’t mind dulling your saw.

[jpc]

Whatever you do, do not re-wet the rock unless you don't like your fossil.  This stuff degrades very quickly when it gets wet.