Can anyone help me identify these sandstone 'nodules' please?

[Badger Watching Man]

Nice one!

Actually, sand-filled petrified scotch eggs is a remarkably accurate description...

[Badger Watching Man]

I realise it is probably bad form to answer your own questions on here, but I think I've found the solution to the mystery. I present it here for the curious.

I got in touch with the Bedford and Luton Geology Group, and I must say that they were incredibly friendly, helpful and informative, especially since I dropped the question on them from nowhere.

Here's what they said:

"What you've found are ironstone nodules from the Woburn Sands. They're quite common and they appear in all sorts of shapes and sizes, although tear-drop, flask-shape and round forms predominate.

Their formation is complex, involving the precipitation of iron-rich minerals around a nucleus of sand grains, fossil fragment or pebble. The happens soon after the sand was deposited on the shallow sea floor, whilst it still contains plenty of dissolved minerals. Nobody is quite sure why some nodules retain a 'soft-centre' of sand grains, but it suggests that the precipitation process worked from the outside inwards, and never infilled the whole body.

Some nodules have several crusts, often of different colour and composition (the manganese-rich ones tend to be purple). This suggests more than one phase of precipitation.

There are plenty of articles and pictures about nodules on the internet, although the scientific explanation about their formation is often wooly. They're popular because they create such interesting forms and they are known from many stratigraphic horizons and different environments throughout the geological record."

So there you have it. There's still an element of mystery, but big thanks to the B&LGG from me.

[LynM]

Thanks for sharing that, Badger. Good for you to find the geology group and good on them for a detailed but understandable reply.

[Meta menardi]

Bad form? Posting photos of ................. might be, but very little else is.

No phone messages to .... I don't have to complete this.

[Gill Catton]

fascinating! Thanks for sharing that info I shall know now if I ever see them!

[Pete Collins]

Thanks, that was very interesting Badger Watching Man.

I've walked along the Greensand Ridge in Bedfordshire too (there's a long-distance path along it), but I don't think I came across any of those nodules. If I go back there, I'll look out for them.