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Macrophyseter

So I'm aiming to visit some of the Altamira Shale (Monterey Formation Shale) exposures in my city and try to find some fossils in fallen shale pieces. However, I simply cannot find a good way to split shale (I also have small rocks of Altamira Shale in my backyard, which could be seen as a sort of "practice"). The shale that I get are usually very hard and compact, as seems to not crack very easily with the materials I have. I don't have a real chisel, but I makeshift them (nail, screws, and screwdrivers). When I use them, it seems to just dig a hole in the area where I'm striking at and creates no cracks. Does anyone who has experience with Monterey Shale know the best way to split a shale like this, preferably clean in half?

 

(It seems that the rocks I'm trying to split are the exact same rocks found in any other part of the Monterey Formation, like Jalama Beach)

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I have found the Monterey Shale I encounter does not split in clean layers like you would enjoy. Rather breaks into squarish chunks similar to safety glass.

Your area may experience it differently.

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It would depend on the bedding planes and how well they are fused. Also if the formation has had stress that caused some cross bedding fractures.

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Fossildude19

Sometimes, shale just doesn't want to split nicely. Often it can be cross-bedded, with no distinct cleavage planes. 

You really cannot expect to do a decent job without chisels, though. :( 

 

Harbor Freight has some relatively cheap cold chisel sets. 

Save up, if you have to, and buy a set. 

Sometimes trying to do a job with the wrong tools just isn't worth the effort.  

 

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Yeah, 'paper shales' (like from the Florissant fossil beds) can be split with a razor blade, but in massive shales you have to work hard to even find a bedding plane.

Sounds like the Monterey is of the latter. The fossils will mostly be on the bedding planes, and whacking the edge of thicker pieces might reveal those planes by cracking.

Add safety glasses to your kit before you pick up the hammer again, though! Please?

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Also depends on the size of the block being split. A big block requires chisels to tease out the bedding plane. Being careless means the shale will just fracture. I use a sledge to reveal those with taps, and then move to chisels. Some shale is more dense than others.

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Brett Breakin' Rocks

  I've also had varying degrees of success with a wide brick chisel matched with a 3 lb hand-sledge to help distribute the blow/force and avoid carving a hole with a smaller head chisel.  You might also try sharpening the chisel head .. filing it down to a sharper point.  That has also helped in the past.

 

bon-tool-chisels-11-192-64_1000.thumb.jpg.f8c5275edc6e6e0d74a06cc102d5c097.jpg

 

Cheers,

Brett

 

PS. I guess you could always lug a promising chunk home and let mother nature run its course.

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DevonianDigger

Have you tried freeze/thaw on that material?

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Peat Burns

I am not familiar with the deposit that you are working, but rarely do I leave home without a piece of Kemmerer, WY, ingenuity, just in case I need it.  This is what the fossil fish folks there call a "steel".

 

20180607_221224.thumb.jpg.aee4cf6b0900d63464ff6a7bcd5c213c.jpg20180607_221220.thumb.jpg.fb990e375d2d9eef3e1016563542c74c.jpg

 

Naturally, it works great in the Green River Formation material, but I have found that it has uses elsewhere.  I've even used it in the somewhat "blocky" material at Penn Dixie with enough satisfaction that I didn't want to trade it for another tool.  I like to let everybody else work up a sweat and spend hours digging out massive virgin blocks while I sit in a lawn chair on the spoil piles created by previous fossil hunters splitting their refuse and finding the treasures they missed :)

 

These are made of hardened steel and beveled on one end.  The bevel is on *one face only* (not both faces of the tool).  You whack this thing into the stone with a hammer from the non-beveled end.

 

 

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AncientEarth

The type of chisel that Peat showed are what you need, skip harbor freight...been there and done that. Same result with a thick chisel as with the screw driver - end up just driving in a hole rather than split anything. 

A technique I sometimes use is "scoring" on the rock, you can create fractures and gently tap around the block to "guide" the break where you want it with a simple sledge hammer. 

 

Altamira Member is a very siliceous shale due to volcanics, unlike other sections of the Monterey. You can break off large slabs and let them air dry for a couple weeks, or use a very strong, but thin, chisel. 

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On 6/7/2018 at 7:22 PM, Fossildude19 said:

Sometimes, shale just doesn't want to split nicely. Often it can be cross-bedded, with no distinct cleavage planes. 

You really cannot expect to do a decent job without chisels, though. :( 

 

Harbor Freight has some relatively cheap cold chisel sets. 

Save up, if you have to, and buy a set. 

Sometimes trying to do a job with the wrong tools just isn't worth the effort.  

 

 

Great advice, Tim.

 

Jess

On 6/7/2018 at 10:24 PM, Peat Burns said:

I am not familiar with the deposit that you are working, but rarely do I leave home without a piece of Kemmerer, WY, ingenuity, just in case I need it.  This is what the fossil fish folks there call a "steel".

 

20180607_221224.thumb.jpg.aee4cf6b0900d63464ff6a7bcd5c213c.jpg20180607_221220.thumb.jpg.fb990e375d2d9eef3e1016563542c74c.jpg

 

Naturally, it works great in the Green River Formation material, but I have found that it has uses elsewhere.  I've even used it in the somewhat "blocky" material at Penn Dixie with enough satisfaction that I didn't want to trade it for another tool.  I like to let everybody else work up a sweat and spend hours digging out massive virgin blocks while I sit in a lawn chair on the spoil piles created by previous fossil hunters splitting their refuse and finding the treasures they missed :)

 

These are made of hardened steel and beveled on one end.  The bevel is on *one face only* (not both faces of the tool).  You whack this thing into the stone with a hammer from the non-beveled end.

 

 

 

 

I got to get me one of those.

 

 

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AncientEarth
2 minutes ago, siteseer said:

I got to get me one of those.


Robert from Wyoming Fossils sells them, I got a full set of thin and thicker gauge ones, used them this week on some Monterey shale and am never looking back. 

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On 6/7/2018 at 8:16 PM, Brett Breakin' Rocks said:

  I've also had varying degrees of success with a wide brick chisel matched with a 3 lb hand-sledge to help distribute the blow/force and avoid carving a hole with a smaller head chisel.  You might also try sharpening the chisel head .. filing it down to a sharper point.  That has also helped in the past.

 

bon-tool-chisels-11-192-64_1000.thumb.jpg.f8c5275edc6e6e0d74a06cc102d5c097.jpg

 

Cheers,

Brett

 

PS. I guess you could always lug a promising chunk home and let mother nature run its course.

 

Yes, that is the kind of chisel I've used working the Aguajito Member of the Monterey (Late Miocene, approx. 10 million years ago).  A wider blade like that is best, and yes, you should sharpen it probably before every trip.  You want to be able to resplit a nice, big piece as thinly as you can.  I should add that it can be a waste of time resplitting because you can find something nice (crab or fish or leaf impression) on one surface but there's little to nothing elsewhere in a plate that might cover the same total area as a pizza and be several inches thick.

 

The Monterey is different even in the same site because you can get shale that splits rather easily into decent-sized plates or it can be very hard (more of a chert) a little higher or lower, breaking up into chunks with loose sediment in between.  The hardest stuff seems to be less fossiliferous anyway.

 

Jess 

 

 

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There's about as many ways to split shales as there are shales, to be honest! Loads of good advice here, so I'll just add one more suggestion...

 

For stubborn mudstone that just keeps flaking, try tapping the edge with the heavy end of your hammer, gently and persistently, while moving it around. Use an anvil (i.e. another rock, harder than the one you're hitting!). The idea is to get the shock waves to propagate through the rock and join up inside; a single hard tap will shatter it, but lots of gentle ones sometimes tease it apart.

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