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angeb20

Any ideas of what this is?

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angeb20

I found this yesterday in a field in Southern Central Minnesota. The field borders a prairie pothole lake. I also found a small shell impression in a sedimentary rock there in the past. In the photos there are 2 like impressions that continue around the piece. Appreciate your thoughts. Thank you.

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GeschWhat

I don't know what this is, but it is really, really interesting. I'm thinking it is geological, but there are plenty of people here that know way more than me. :popcorn:

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ynot

Welcome to TFF!

Can You retake the 3rd picture under better light?

Does this "fizz" when You put a drip of vinegar? If yes, what part(s) fizz?

 

I think it is calcite veins with limestone.

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angeb20

On the smooth areas it does fizz with vinegar. Here is a hopefully better picture although it is the more grey/white color than the yellowish the sun shows. Thanks!

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ynot

Can You scratch a knife with the rough part?

Fizzing indicates limestone for the gray (smooth) areas.

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angeb20

The rough part scratches easily with a knife. So, you think that this was a calcite material that settled into a space between a different kind of rock that created a strange pattern?

(in a novice nutshell) :) 

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Paciphacops

The rough part looks like it could be gypsum.

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LordTrilobite

A very interesting shape. Looks geologic to me too though.

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fossilized6s
2 hours ago, angeb20 said:

The rough part scratches easily with a knife. So, you think that this was a calcite material that settled into a space between a different kind of rock that created a strange pattern?

(in a novice nutshell) :) 

That is correct. Looks like a piece of a giant 'thunder egg' i find. Definitely calcite filled void. 

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angeb20

Thank You Very Much | Clipart Panda - Free Clipart Images

 

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ynot
3 hours ago, angeb20 said:

The rough part scratches easily with a knife. So, you think that this was a calcite material that settled into a space between a different kind of rock that created a strange pattern?

(in a novice nutshell) :) 

Limestone (grey parts) is a calcium carbonate. It is easily dissolved by acidic groundwater, leaving voids that can be filled with other minerals. These minerals can be layered (like a cake), and partially or wholly fill the void.

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angeb20

Do you think this find is along the same theory? Possibly a rock or petrified wood outer surface filled with a caked sediment.... (found along the same small lake)

Thanks again :) 

 

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ynot

This looks more like a metamorphic sandstone called quartzite.

Would like to see some close up pictures of different areas.

Also- does it fizz? Can You scratch it with a knife?

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abyssunder

I'm thinking of a partial septarian nodule for the first specimen, considering the double-wall structure.

 

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picture from

 

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ynot
12 minutes ago, abyssunder said:

I'm thinking of a partial septarian nodule for the first specimen,

That does fit well with the piece.

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angeb20
1 hour ago, ynot said:

This looks more like a metamorphic sandstone called quartzite.

Would like to see some close up pictures of different areas.

Also- does it fizz? Can You scratch it with a knife?

 

The outside of my 2nd piece is very hard and the inside is a much softer material like it settled there. I will try for closer pics, my camera hates close up pics though. I think I agree on quartzite.... 

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