No (Dan), I don't know; at least not off the top of my head. (But thanks for the vote of confidence!)
It reminds me of a fine-grained red siltstone I saw in northern Spain back in 1977. That had very fine lamination, shown by subtle colour contrasts; the laminations were very contorted; clearly it had been liquidized and mobilized since it was deposited (and before it became lithified, of course).
But I don't want to jump to conclusions.
Highly intricate flow structures can also arise in industrial slag - where some mineral and/or by-product and/or waste becomes molten, gets spilled or raked-off, and cools - leaving its inhomogeneities showing how it had been swirled around before it set.
So, some questions:
- where did it come from (as accurate as you can)?
- did you pick it out of solid rock or was it lying loose?
- if lying loose, in what situation?
- if from solid rock, what was that rock like?
- were there other lumps like this one? many?
- does it seem heavier or lighter than you'd expect for an average sort of rock of its size
- is a magnet attracted to it?
- is a steel knife attracted to it?
- if you scratch it along the back (rough side) of a ceramic tile, what colour mark does it leave?
- does it 'ring' if you hit it with a hammer (as if it was metal), or does it give a duller noise?
Thanks for the info and further photos.
In principle, it could be either:
- haematite, or
- iron-rich industrial slag.
Haematite does occur with a banded structure (see http://en.wikipedia.org/wiki/File:MichiganBIF.jpg, linked from http://en.wikipedia.org/wiki/Hematite). But the banding never has the degree of contortion shown in your specimen.
Your sort of banding might occur in lava (especially some rhyolites), but it would not be sufficiently iron- (or nickel-) rich to attract a magnet.
So I think it is a piece of iron-rich industrial slag. As such, the banding would be due to different materials in the melting pot, as it were, and the convolutions due to flow, eg. due to stirring/pouring/etc.
Rather a nice piece, as they go - good find.
If there is a local history museum in the area, they might be able to comment.
If you Google 'Cramond slag', you'll find some mentions, eg. 'iron slag in the river' at the site of Cockle Mill (http://www.cramondassociation.org.uk/historic_map.htm).