Fossil or rock

[Ben&Jess]

Thought this might be flint but don’t get the the outside shell of the object, thoughts???

[Ben&Jess]

[Dryptosaur]

Looks like flint.  Could be Dover flint, it was used as ballast often years ago.  English ships would fill up with it and dump it when loading up goods from the colonies.

[D.N.FossilmanLithuania]

chert nodule

[Mark Kmiecik]

The outside is how the inside will look after it has been exposed to wear and reaction with other minerals over a period of many years.

[grandpa]

Hi B&J.  I agree that this is a chert nodule. 

As to the "crust" or outside skin, think of what chert is and how it is formed.  Chert starts out as a super-hot liquid silicious ooze that enters a rock substrate already formed and fills in the vacancies in that substrate.  An example would be a limestone substrate with gas pockets.  The super-hot liquid fills the void and begins to cool and solidify.  As it does so, at the interface with the host rock, a chemical reaction takes place (consider it a metamorphic interface) and forms what I'd refer to as the crust or skin.  That's at least how I picture it.  If I am wrong, I'm sure there are petrologists in the group who can come along and teach us both something.  That correction aside, for now that's my story and I'm sticking to it. 

[Mark Kmiecik]

4 minutes ago, grandpa said:

Hi B&J.  I agree that this is a chert nodule. 

As to the "crust" or outside skin, think of what chert is and how it is formed.  Chert starts out as a super-hot liquid silicious ooze that enters a rock substrate already formed and fills in the vacancies in that substrate.  An example would be a limestone substrate with gas pockets.  The super-hot liquid fills the void and begins to cool and solidify.  As it does so, at the interface with the host rock, a chemical reaction takes place (consider it a metamorphic interface) and forms what I'd refer to as the crust or skin.  That's at least how I picture it.  If I am wrong, I'm sure there are petrologists in the group who can come along and teach us both something.  That correction aside, for now that's my story and I'm sticking to it. 

I agree. Also a possibility. The sample would need to be chemically analyzed to determine which is the case. If you have a vested interest in making the distinction, go for it. Otherwise it's not worth the time, or just not necessary. Depends on how badly you need to know.

[Ben&Jess]

Gents thanks for the info and thoughts. Being from up north it was very common to find chert or flint in creeks or anywhere the out croppings showed up. We have just not seen it down here or at least I haven’t so it caught us off guard  

[doushantuo]

One of the more influential chert papers is this one:

Chert is one of the more interesting lithologies you can find.

Rhynie,Monterey,the influence of chert on seismic interpretation,porosity,itspossible origins,and the biota it contains

[Ben&Jess]

So your suggesting possible seismic activity brought this to the surface??? that’s interesting. Especially considering tomorrow we are having a regional earthquake drill. Have always been intrigued by all the buildings around Chucktown that have the modified supports added to them after the 1886 quake 

[doushantuo]

No.that's ABSOLUTELY NOT what I'm saying.

[doushantuo]

E.G.:

 

 

Notice particularly the length scale of the layer.

Chert influences submarine slope stability(think oil rigs or offshore windfarms).

Now think of the siliceous bioproductivity that such a layer implies

Please note,BTW,the vertical exaggeration

This particular silica layer is influenced by polygonal faulting,hence the slightly rough topography

 

 

 

 

 

 

 

 

 

 

 

 

[Ben&Jess]

My apologies I only skimmed your message and now understand your thinking of the possibility of chert showing up in thin beds and that I do see that in marine layers  in Texas and SC chert has been found. This I did not know 

[Ben&Jess]

Your reference to the bedded jasper paper makes sense to of the 5 or 6 pieces we have found none larger than the palm of my hand they are reddish yellow which would lead to the jasper chert idea