Weird Rock

[Doifhg]

Was making a new compost heap for my folks and struck this weird looking rock about 3ft down. I don't think it's a normal sediemntary rock, at least I haven't seen any around here with deposits like that in it? And it has the odd sratching on the side.

Any opinioms on this?

 

[gsimonel]

It looks like it contains a fossilized impression of some rugose coral. Whereabouts do you live? Do you know the age of the rocks in your area?

 

[Minamii]

It's a fossilized shark tooth.