FOSSIL ?

Hello is there anyone here that can advise me on what I think is a Fossil 

It weighs 1143 g

18cm X 17cm 

It seems that only one photo can be attached

Thank you. 

 Molly

Select reply and you can add more photos.

 

Looks like the shape of a Nautilus.

What size is it ?

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18cm diameter weighs over 1kg

it is about 1" thick 1.5 in some places

Sorry, just realised you had the size in the OP.

 

imagesooo.jpg download.jpg

 

Could be about the size of a Nautilus and perhaps coral encrusted or just fossilized.

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It looks as though it might be an open clam

 

 

Yes looks like you are closer to the mark.

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Thank you for your replies

I found this Prehistoric Clam Shell do you think my one could be like this ?