When I was fossil hunting in Sandown IOW as a kid my teacher said that often fossil sponges are often found encased in flints especially spheroid ones.
We found several including one that was hollow with the sponge like fossil rattling about inside. There was a bump on the outside which we presumed was the stem of the sponge.
This item was found in a garden in london.
Two different views of the same rock.
In some cases the sponges in flints are more nearly spherical, but being irregular does not rule out the possibility. It would be necessary to put it under a hand lens or microscope, hoping to see evidence of cellular structure and/or spicules. In other cases, there is not much left of the sponge; the centre of the flint may be 'rotten'. The process of 'rotting' (actually more of an inorganic decay that rotting) can remove much of the evidence. So even with a magnifying device, it may not be possible to see enough evidence to say one way or the other.
Glad to see you still online after my winter break. Cannot wait to get back to my evening moth hunting again so expect some pictures soon.
I will endeavour to get a close-up of the central portion when I next see my neighbour who was the finder of the item.
Meanwhile I am trying to recover fossils that were in my collection at my primary school which I maintained until I left in 1958. Hopefully they stored them with the Victorian natural odditities case that was a centrepiece of the school hall. There is a pair of strange iron pyrites objects about 3" long that I found that looked for all the world like a brown mushrooms. If I cannot find them at the school I`ll post a drawing.
Very interesting find, I agree with Mike and think it 'could be' a sponge.
I hope it's ok as I have attached some images of sponges/corals that also 'could be' from the Holderness coast, East Yorkshire.
Many thanks for your comments and the pics. I am no expert so I cannot really comment on them but they are very odd and I have seen many similar items. Are they in chalk and could some of them be tracks of some kind of burrowing worm. Was wondering if MikeHardman had any comments on them.
Yes, they will be from chalk. Seeing as how flints come in such a wide near-randomness of shapes, the particular shapes of individual specimens usually does not warrant discussion. But there are some characteristics that crop-up commonly. They includes cavities. Some cavities/depressions are filled with chalky flour, some of them are lined with crystals (geodes). In some cases the rotten core is known or thought to be the remains of a sponge. Other fossils can be found in flints. The external form of flints in some instances arises from the siliceous material filling animal burrows before turning to flint. The processes that form flint are not perfectly understood, even today. Consequently, there are some features that we are still guessing about. Internal banding is one of those. Co-called 'banded flints' are often mistaken for fossils. If you search for 'banded flint' in NaturePlus, you'll find many examples, along with explanations.
Good photo, thanks.
There seem to be shell fragments in the core; the fragmentation is curious; the original fossil could have been a sponge but I cannot see any pieces that are clearly so. Logically, one might wonder if it is coprolitic.
I think your specimen could be called flint meal? these are sought after by micro fossil collecters because of there small fossil content.
I am probably wrong although we have found a couple of similar specimens on the Holderness coast.
You need a microscope to have a closer look.
I called it 'chalky flour', the proper term 'flint meal' not having dropped into my thought processes while I was typing! Thanks for picking me up on it. I thought the fossil fragments in Ray's specimen were on the large side for flint meal, but I guess I don't know the upper size limit.
Ref on flint meal (one of several):
Many thanks for your observations. I have never heard of `flint meals` and was away unti l tonight so I havn`t had time to dig out my microscope and it`s usb photo attachment but will do so tomorrow. Meanwhile I`ll do some research about flint meals and post when I`ve got some photomicrographs. At very high magnification it works best with direct sunlight. I did think that maybe I could polish the specimen flat but that would be beyond my ability but it may reveal more detail and also might destroy some of it as well. Have not got a binocular microscope but I shall play around and see what I can get.
Hi Mike & Tabfish,
First an apology to have left this one hanging but I`ve been laid up a bit with a nasty cold.
From what I can see the item has no chalk in it at all. The centre part has no regular shapes that resemble microfossils and at 80 X magnification I could see nothing of interest. I even applied a little weak acid to it and it seems the whole thing is silicaceous. No bubbles or signs of reaction at all The white parts in my original photograph are I believe to be light artefacts from the flash I used at the time. They are just chips at the points where the flint has fractured and thus at a different angle catching the light in a peculiar way. Their are several different coloured layers and what could be a stem. I have put in a number of shots using my Webcam microscope as 80X shots with my microscope are distinctly uninteresting. Let me know what you think. If it I get the free time I may pop into the NHM and see if I can get an opinion there. The black marks wavy lines are peculiar and I hardly noticed them until iI
uploaded the photos. If you want me to focus on a particular part of my first or second posted photo then let me know.
Thanks for the further photos.
The siliceous nature suggests flint itself or munged remains of a siliceous sponge. One might argue that the tiny bright (and maybe the black) lines are remnants of sponge spicules, but the general granularity of the area makes me think it unlikely such fine structures would survive.