[chris (OP)]

I was walking in the fields here in Cambridgeshire the other day and picked up this interesting piece. I'm wondering if anyone can explain to me how this pattern forms?

CHRIS-STONE.jpg (801.88 kB . 2431x2524 - viewed 5735 times)

[chris (OP)]

One suggestion on Twitter is "fossilised clay", although even if that is the identification of the stone, it doesn't explain the mechanism of its appearance, which I am eager to know...

[Colin2B]

...... it doesn't explain the mechanism of its appearance, which I am eager to know...

This is a guess, but it looks as though the soft clay has been lying on a bed of pebbles.

[chris (OP)]

This is a guess, but it looks as though the soft clay has been lying on a bed of pebbles.

A good thought. Thanks.

[pensador]

I was walking in the fields here in Cambridgeshire the other day and picked up this interesting piece. I'm wondering if anyone can explain to me how this pattern forms?

CHRIS-STONE.jpg (801.88 kB . 2431x2524 - viewed 5735 times)

It might be caused by trace fossils of something like worms. The cambridgeshire area I think is formed from sediments both from marine and river deposits. The marks might be caused by something like prehistoric lugworms unless of course its soft clay thats been laying on a bed of pebbles and not a fossilized piece of rock.

[chris (OP)]

unless of course its soft clay thats been laying on a bed of pebbles and not a fossilized piece of rock.

No, it's a hard chunk of stone!

[chris (OP)]

I'm definitely liking Colin's suggestion of impressions made by gravel sitting on softer silt or mud and leaving marks.

[chris (OP)]

@Bass is usually the right authority for these sorts of questions!

[Bass]

The polygon patterns make me think this is organic in origin, possibly fossilized coral?

[chris (OP)]

Fascinating. I'd not thought of coral but you're absolutely right that the shapes are all broadly the same but different sizes, arguing for some kind of "growth". I'll go hunting for some images online...

[chris (OP)]

PS - I think @Bass you trump the @Colin2B gravel in clay hypothesis!

[chris (OP)]

I found this on https://www.fossilera.com:

Looks VERY similar, so I think you've hit the nail on the head @Bass

[Petrochemicals]

It looks like hexagons to me, straight lines,  most efficient construction method I believe

[Colin2B]

PS - I think @Bass you trump the @Colin2B gravel in clay hypothesis!

Trump? Trump?
How dare you use that foul word sir? I fear this means rocks at 50 paces.

Not clear from your photo, but do you have any of the central raised pips? There might be one or two lower left, but upper left the hollows look smooth and rounded. Odd that the hollows appear to be of different sizes, does that happen with coral fossils? Is there anywhere the rock is split perpendicular to the surface so you could see whether the pattern goes through?
Would be useful to know age of rock, I was looking for details of local geology and local societies, might be a clue there.

It looks like hexagons to me, straight lines,  most efficient construction method I believe

Yes, but it also occurs incidentally whenever items are packed together eg honeycomb.

[Petrochemicals]

It looks like hexagons to me, straight lines,  most efficient construction method I believe

Yes, but it also occurs incidentally whenever items are packed together eg honeycomb.

It could be made by the same process that produce d the giants causeway, maybe even by the same giant.

[Colin2B]

@

It could be made by the same process that produce d the giants causeway, maybe even by the same giant.

More likely his next door neighbour, the gnome
Unless @chris is a lot bigger than we assume 

[Bored chemist]

Trump? Trump?
How dare you use that foul word sir?

There are much ruder words for a fart.

[pensador]

It looks like hexagons to me, straight lines,  most efficient construction method I believe

Yes, but it also occurs incidentally whenever items are packed together eg honeycomb.

It could be made by the same process that produce d the giants causeway, maybe even by the same giant.

Unlikely, the giants cause way is due to cooling volcanic rock. This is most definately organic in nature, I had been thinking along the lines of pipe rock, but with hindsight it is a piece of coral, as mentioned above.

If global warming raises the sea levels maybe cambridgeshire will go under the sea again, and corals will grow there again. But then again since the acidification of the oceans is increasingly killing of the corals, maybe corals will eventually become extinct.

[pensador]

Trump? Trump?
How dare you use that foul word sir?

There are much ruder words for a fart.

A Trump might be a fart in England, but a Johnson is something you pee with in America.
 

[Bored chemist]

Trump? Trump?
How dare you use that foul word sir?

There are much ruder words for a fart.

A Trump might be a fart in England, but a Johnson is something you pee with in America.
 

And I'm not sure which is funnier.