Porphyry Stone contains a fossil?

[Dargos]

Hi

I found this 2 days ago with other lovely stones, cleaned them with soap and then i found this look a like trail of clam fossil (or maybe it's clam fossil inside the rock itself, not sure about it).

I know it's unusual to find a Porphyry Stone with a fossil and i still think it could be my imagination, i even put the stone on some acid and this thing didn't fade away at all.

Anyway here some photos for you to share your experiences or thoughts about it. (if you require more or even a video just request it).

[Rockwood]

9 minutes ago, Dargos said:

I know it's unusual to find a Porphyry Stone with a fossil and i still think it could be my imagination

I've collected quite a few brachiopod fossils in volcaniclastic rock. I don't recognize it here though. These look more like shell bits to me.

[Mahnmut]

Hello Dargos,

I think there are lots of shells in that stone, most of which you see only in cross section, the one that caught your eye is only oriented more parallel to the surface than the others.

How sure are you about the ID of the rock, it being porphyry? Porphyry is defined by its texture, including bigger chrytals in finer matrix. 

All the bigger clasts I see in your specimen seem to be shells.

So my question is, is the matrix igneous indeed or sediment after all?

I have often wondered what happens to shells and bones that are enclosed by magma/lava. There are precedents.

Best Regards,

J

 

[Fossildude19]

This looks more like chert or dolostone, rather than porphyry. 

Definitely filled with shells, though.

[digit]

Indeed. This stone is packed with shells but the rock matrix does not seem to be porphyry which solves the mystery of having fossils in an igneous rock.

 

https://en.wikipedia.org/wiki/Porphyry_(geology)

 

 

Cheers.

 

-Ken

[Dargos]

Well... I was wrong specifying the stone (i'm completely new to this world and i'm so excited that i even destroyed some dendritic stones i found with acid )

Now after good looking i can see well other shells here and there.

Also those are some of weird looking rocks i found, maybe someone can notice some other interesting details (some of them have holes because of the acid so they aren't quite clear to see the inclusion, and sometimes the holes are the inclusion destroyed.. Sorry).

(12 photos, 5 stones)

[digit]

6 hours ago, Dargos said:

(i'm completely new to this world and i'm so excited that i even destroyed some dendritic stones i found with acid )

That's one way of learning.

 

The stone with the concentric circles appears to be some sort of concretion. Many of the other stones appear to be cherty (microcrystalline quartz) which make them shiny/glassy and leave sharp edges when fractured. Not seeing any really obvious fossils but at least one seems to have a tubular inclusion that could be something like an orthoconic nautiloid or a belemnite. Not familiar with the rocks and formations where your items are found so this is only a guess.

 

 

Cheers.

 

-Ken

[Rockwood]

I'm not seeing anything that looks all that convincingly volcanic. If that was in question at all.

[Mahnmut]

The second one has fossil inclusions, cannot tell what though, maybe with closeup photos. If these are beach or river pebbles, they may come from very different sources.

Some general advice: use acids only when you know what material you are dealing with (or a careful drop to test). I learned this the hard way when a chromate mineral started to produce clouds of chlorine gas under HCl.

When posting multiple items in one thread its helpful to number them, simply write the numbers on a sheet of paper and put it in the photo. Makes answering easier.

Best Regards,

J

[Dargos]

Thank you all friends, i really learned a lot from you ❤️