Mystery river rock - fossil or no?

[Wrangellian]

My aunt found this on the Chemainus River recently. Usually I can tell if something is a fossil even if I don't know what kind of fossil, but this one has question marks all around it. The rock looks like flint to me (at least chert - we have lots of chert around here but actual flint is not something we see very often here on Van Isle, so I'm not sure of that either). As you can see it is in the process of being sliced, so there is one cut surface to look at there, opposite the one that is glued to the wood block (pics 3 and 5). The glossy look is partly due to the rock saw oil still covering it. It is quite fine-grained in the 'bubbly' looking area anyway.

Is there any sort of fossil that could account for the 'bubbles'? (e.g. sponge, radiolarian...? - just shots in the dark), or is it purely geological? Do I need to get microphotos of the inclusions for an ID? (That could be difficult - I could try a macro lens on the camera).

 

 

[Wrangellian]

No ideas? Who do I need to tag? @FranzBernhard @TqB

[TqB]

I don't think the blobs are fossils; the fine bedding seems to run right across  them. It does look like a chert which often shows haloes like that - I don't know the cause. (In Europe, "flint" generally refers to the particular kind of chert that is abundant in the Cretaceous Chalk but I think you have a different usage over there.)

Like many cherts, it might contain sponge spicules.
 

[FranzBernhard]

2 hours ago, Wrangellian said:

Who do I need to tag?

Thanks, but sorry, no idea!

(Well, I don´t tell you, that it looks somewhat like "snowflake obsidian" to me...)

Franz Bernhard

[Wrangellian]

2 hours ago, TqB said:

I don't think the blobs are fossils; the fine bedding seems to run right across  them. It does look like a chert which often shows haloes like that - I don't know the cause. (In Europe, "flint" generally refers to the particular kind of chert that is abundant in the Cretaceous Chalk but I think you have a different usage over there.)
Like many cherts, it might contain sponge spicules.

OK, thanks. I always understood flint to be a very fine-grained type of chert, i.e. microscopic grains, so the rock looks almost glassy, as this stuff does to my eye, but I stand to be corrected. (There is a coarser-grained layer, as you can see, which I assume is stratigraphically below the flinty layer). If it came out of the Nanaimo Group rocks upstream, it would be Cretaceous in age.

I wonder what the whitish grains are at the center of the haloes....

[Wrangellian]

49 minutes ago, FranzBernhard said:

Thanks, but sorry, no idea!

(Well, I don´t tell you, that it looks somewhat like "snowflake obsidian" to me...)

Franz Bernhard

Thanks anyway! The resemblance to snowflake obsidian wasn't lost on me... My aunt is into lapidary and this kind of thing would naturally appeal!

[Wrangellian]

Here is a scan of the end slice that I polished, if it helps. I still can't tell what those light-colored spots inside the haloes are. Oh well. I guess it will go into my geological collection.

 

Edited July 11, 2023 by Wrangellian