Fossil Or Funky Stone?

[ivetavai]

[FossilDAWG]

I'd go with "funky stone". In fact, the conchoidal fracture you can see in the top right photo suggests a flint nodule.

Don

[Kosmoceras]

No, this is a fossil. A fossil sponge in flint. I come across these a lot in locations I visit.

[painshill]

Yep... Thomas is quite right. It is flint (proper European flint, as opposed to what Americans call flint). When it comes out of chalk and occurs in nodules which are odd funky shapes or have holes in them, this is very frequently because they are fossils of some kind or silicated replacement bodies in cavities left behind from something organic. Sponges and echinoids are most common but also sea-bed detritus of every kind. Also casts of burrows from marine worms, burrowing shrimps and so on... that's often what the odd finger and tooth-like shapes are. Flint doesn't just randomly take on these odd shapes... there's normally a reason.

[Kosmoceras]

A few of those I have found.

[Auspex]

It qualifies as a "funky fossil"

[FossilDAWG]

No, this is a fossil. A fossil sponge in flint. I come across these a lot in locations I visit.

So, we all agree on the flint nodule part. I'm in total agreement with Painshill that such nodules may be replacements of sponges, but also burrow casts and "all manner of sea bed detritus". I used to find these nodules in the chalk when I lived near Maestricht in Holland, so I'm somewhat familiar with them. So, can you tell me what it is about the specific specimen in the photos that is diagnostic of a sponge, and excludes it being a burrow cast or any of the other myriad things that nucleated flint nodules? I'd appreciate it of you could point to features that are indicative of some particular genus or species of sponge. I ask because I'd like to learn; it looks like a burrow cast to me, but I could certainly be wrong.

Don

[ivetavai]

Thank you very much guys. However this is all very scientific for me! What is flint? More pics? It looks very much like a snakes skull to me and fossil formed inside of it...can that be possible?

[ivetavai]

Oh and this is found in Hunstanton, Norfolk, UK. Think there is some chalk clifs too

[Kosmoceras]

It has the typical features of a sponge such as Ventriculites. The structure of the fossil (quite rough) gives it away, and it has some holes in, typical with the top end of a sponge.

I have no idea about burrows; maybe painshill can inform you about them, but from what I see, the features say sponge.

What I like about this forum is that you learn something new every day.

All the best,

Thomas.

[Kosmoceras]

Thank you very much guys. However this is all very scientific for me! What is flint? More pics? It looks very much like a snakes skull to me and fossil formed inside of it...can that be possible?

Flint is a hard gray rock consisting of nearly pure silica (chert), which is found in chalk. Silicon is the second most common element one can find on Earth.

The fossil is inside of it, but it becomes a nodule when it is encased in stone. Kind of like if you get a stone and role it in snow, making it bigger and bigger. To get back to the stone you must split the snowball open. But with sponges, they are very fragile and will break if split.

Bones are very rare in flint, not sure if I have ever heard of any to be honest, there is little chance of it being a skull, for sure a sponge.

"The majority of silica found in flint nodules is biogenic (produced by living organisms or biological processes). Although today's flint nodules are inorganic, the silica that formed them was originally sourced from the remains of sea sponges and siliceous planktonic micro-organisms (diatoms, radiolarians) during the late cretaceous period (60-95 million years ago). Flints are concretions that grew within the sediment after its deposition by the precipitation of silica; filling burrows/cavities and enveloping the remains of marine creatures, before dehydrating and hardening into the microscopic quartz crystals which constitute flint." Source

More information about flint - Link

[Kosmoceras]

I have the answer. Flint burrows are more shaped, elongated and sometimes branching, while flint sponges are more textured.

Link- (open document).

[sward]

I wouldn't care even if it wasn't a fossil. I would have picked it up as well and added it to my collection just because it's so "funky".

Nice find.

[Herb]

OK, excuse me, but what is 'proper' European flint as opposed to what we Americans call flint?? One of the largest flint deposits in the world is Flint Ridge in Ohio. Chert nodules that are dark brown to black can also be called flint. They are both cryptocrystalline quartz. Chert that is found in limestone and chalks is formed by replacement of calcite crystals by chert, still chert, but called flint due to it's color. Laminar deposits = chert; globular deposits = flint, if dark colored. Is this not correct?

[painshill]

OK, excuse me, but what is 'proper' European flint as opposed to what we Americans call flint?? One of the largest flint deposits in the world is Flint Ridge in Ohio. Chert nodules that are dark brown to black can also be called flint. They are both cryptocrystalline quartz. Chert that is found in limestone and chalks is formed by replacement of calcite crystals by chert, still chert, but called flint due to it's color. Laminar deposits = chert; globular deposits = flint, if dark colored. Is this not correct?

Hi Herb

I'm not trying to open a can of worms here, but this one of those areas where not everyone sings from the same hymn sheet. Nevertheless:

The popular use of the term “flint” in a non-geological sense has been influenced more by the users of the materials than by geologists. As a general rule, geologists primarily classify rocks according to what they are – not how they formed – and may further qualify those terms with descriptions concerning formation.

On this side of the big pond, we use the term “flint” for material that originated in chalk formations and the term “chert” for material that originated in limestone… but it’s cryptocrystalline quartz in both cases – or often a mixture of cryptocrystalline and microfibrous quartz in the case of chert. Beyond that, there is a spectrum of possibilities for which the distinctions are non-geological. The more microfibrous the quartz is, the more likely it is that we would term it “chalcedony”. When it has extremely high purity of silica it’s sometimes called “silex”. Jasper is essentially an opaque form of chert coloured by iron oxide inclusions.

For early Europeans, the differentiation between flint and chert embraced a difference in quality. Flint was regarded as higher quality and that’s a function of it being formed in chalk deposits with a particular geological formation history, having a particular water content and being generally derived from silica that originated from sponge spicules. In the New World the distinction based on quality was reinforced by the term “flint” being adopted to also distinguish between differing qualities of local chert. There was also a tendency to use the term “flint” to describe nodular chert (as opposed to chert in massive layers or beds), which generally reflected that same quality difference.

There is - as far as I know - only one deposit in the whole of North America that might be described as “flint” by European terminology… “Georgetown Blue” which comes out of the Austin chalk in Texas. There is also a flint-like nodular material which comes out of the Niobrara chalk in South Dakota.

[painshill]

Very comprehensive reply, Thomas.

Here's a flint nodule which is a cast of a galleried chamber from some kind of marine burrowing animal. Interestingly, this one seems to have been converted into a digging artefact (in Neolithic times) by chipping one of the gallery arms into a blade. Given where I found it, it was probably used for gouging into the chalk to free up more flint nodules.

[Herb]

Thanks for the extra information,painshill, but I couldn't let it pass. European vs American flint.

btw, paleo and woodland indians came from many miles around to get flint materials from Flint Ridge, which is now a state park

http://www.360cities.net/image/flint-ridge-memorial-state-park-licking-county-ohio-usa

Edited July 5, 2012 by Herb

[painshill]

Thanks for the extra information,painshill, but I couldn't let it pass. European vs American flint.

btw, paleo and woodland indians came from many miles around to get flint materials from Flint Ridge, which is now a state park.

Yeah, I'm very familiar with the material... I have a friend in Licking County, Ohio who's a rockhound and artefact collector. It's beautiful looking stuff and high quality knapping material... but if you wanted a good quality gunflint in historic times you'd be looking for European material.

[Herb]

I give!