Caron,

Like Tabfish, I'm having difficulty coming to grips with your specimen.

I see the little cavities that suggest bone to you (alternatively, they could be where mineral grains have fallen out and/or solution pockets from encrusting lichens).

I see the eye socket, but I am not convinced.

I see also the brush-like marks in various directions and the white partial coating.

I see the small slab-like pieces cemented together (not necessarily by cement as such).

This does not strike me as fossil. I think it is man-made, though partly composed of natural rock. Accounting for the white areas and brush-like marks: it may have been painted with road-marking 'paint' at some time, perhaps when it was part of something larger (jerbing, signpost plinth, etc.)

Some local knowledge would be useful...

1. Hanson's have a quarry just north of the A468, at the eastern end of Machen. Perhaps you could take your specimen there for an opinion (go to the main office and ask if somebody familiar with the local rocks could give you an opinion).

2. David Cavell - who gave a talk on the local geology - http://cymdeithastwmbarlwm.blogspot.com/2012/09/twmbarlwm-time-machine-uncovering.html

(this might get you to him - http://www.gfgd.org/groups/leicester)

See also:

- http://www.scribd.com/doc/20701113/Machen-Quarry-extension-Carphilly (includes mention of the geology)

Mike