Interesting rock pattern I found

cocoshovel

Hi everyone. About 12 years ago when I was a kid I was playing in a mound of rocks and dirt (left there by construction workers) near my house when I somehow stumbled upon this rock despite it being covered in muck.
I ran home and washed it thinking I found some amazing dinosaur fossil or something and its been sitting proudly on my shelf ever since. Looking at it now I dont think its a fossil at all, but it would be nice if I was wrong.

If secondary school geography serves me well, it seems to be limestone and the spiral in the centre im unsure of. Marble perhaps.

Anyhow, I just though it would be interesting to share with you guys, and to see if I cold get some input on the spiral and how it could have been formed.
Some things I should note are that I do live about 1 mile from a quarry where a lot of fossils have been discovered in within the last 20 or so years, but the rock up there is a sandy colour and breaks really easily so I dont think they're from the same place. I live in South Kilkenny but the rock could have come from anywhere.

Coles

What a wonderful stone! What's the other side like?

muckish

It's probably a cephalopod mollusc of some description. pretty common fossil from the carboniferous period. The white material is probably calcite crystals. If you dropped some acid on it it should start fizzing.

cocoshovel

Coles wrote: »

What a wonderful stone! What's the other side like?

Pretty much just flat with no marking on it. The stone however sort of sparkles all over. Not sure if you can notice it in the picture.

It's probably a cephalopod mollusc of some description. pretty common fossil from the carboniferous period. The white material is probably calcite crystals. If you dropped some acid on it it should start fizzing.

So it is a fossil then :eek:, nice. About 0.8 - 2million years old. When you say drop acid on it, would any type of acid do such as cola? (might be a stupid question) and will it damage the pattern/stone in any way?

muckish

roughly 360 - 300 million years old for the carboniferous period.
The acid test is what geologist would do to determin the mineralogy. I'm not suggesting you pour anything on it. It wouldn't damage it anyway as you'd only use a drop. It's normally 10% solution of HCL (if memory serves me right!). You could try cola and see what happens.

nkay1985

muckish wrote: »

It's probably a cephalopod mollusc of some description. pretty common fossil from the carboniferous period. The white material is probably calcite crystals. If you dropped some acid on it it should start fizzing.

I just stumbled on this from main so I've no idea about the subject matter. Just wondering why you'd think it's a fossil? You're the white thing in the stone used to be a living thing, is it?

locum-motion

nkay1985 wrote: »

...You're the white thing in the stone used to be a living thing, is it?

What?

nkay1985

locum-motion wrote: »

What?

Yeah thought that wasn't very well put.

Basically asking what in that picture is a fossil. The whole thing? If so, what's the difference between that and any other rock?

cocoshovel

nkay1985 wrote: »

Yeah thought that wasn't very well put.

Basically asking what in that picture is a fossil. The whole thing? If so, what's the difference between that and any other rock?

Im guessing its just the white spiral that is the fossil. The rest of it is just the rock. (could be wrong)

Sundy

nkay1985 wrote: »

Yeah thought that wasn't very well put.

Basically asking what in that picture is a fossil. The whole thing? If so, what's the difference between that and any other rock?

Well its not usual to see spiral patterns in sedimentary rocks like that unless a fossil is present.

you may be surprised to know that fossils like this are quite commonly found in Ireland, especially in waulsortian reef limestone formations.

stoneill

It might be worth pointing out that the fossil we see is the internal shell, as if the shell has been cleaved in half, what you see is a section through the fossil to give the spiral pattern.