Any geologists on here?

[Globalti]

My colleague picked it up on the beach at Aberystwyth, she uses it is a paperweight. I'm no geologist but I'm a mountaineer so have always been interested in the rocks under my feet. This one fascinates me because it has fine white (mica?) veins (sedimentary?) running through it, which have later been fractured and the cracks seem to have been filled with a softer brown crystalline material, maybe something igneous containing iron? It then broke off the bedrock (glacier?) and spent the last couple of centuries trundling down the river to where it was found. I don't know anything about time scales or the names of the three materials present though. Got any ideas?

 

[asterix]

Looks as if it's slate meets granite..

I found a strange rock on the South Downs. Turned out it is a meteorite.

 

[marinyork]

An egg marble taken from a garden/department store and left as a prank?

 

[psmiffy]

Migmatite?

 

[rich p]

Mipancertite, I think, but I'm no expert.

 

[threebikesmcginty]

Marmite?

 

[Fnaar]

Don't know what it is, but it looks Gneiss

 

[XmisterIS]

Kryptonite?

 

[the snail]

what a load of schist

 

[Rhythm Thief]

Water worn rocks are notoriously difficult to identify. An ex of mine got a First in geology from Oxford and was given a lump of water worn rock to identify during the practical exam. It turned out to be a bit of concrete, and not a single one of the Oxford educated geologists got it right.
My geology training was a long time ago, but I'd have said that was an acid igneous rock, possibly granite, containing some quartz veins. Quartz will leave scratches on the flat of a penknife blade, whereas calcite (which looks similar but is found in alkaline rocks such as limestone) won't. But as I say, I'm a bit out of practice ...

 

[Ravenbait]

Water worn rocks are notoriously difficult to identify. An ex of mine got a First in geology from Oxford and was given a lump of water worn rock to identify during the practical exam. It turned out to be a bit of concrete, and not a single one of the Oxford educated geologists got it right.
My geology training was a long time ago, but I'd have said that was an acid igneous rock, possibly granite, containing some quartz veins. Quartz will leave scratches on the flat of a penknife blade, whereas calcite (which looks similar but is found in alkaline rocks such as limestone) won't. But as I say, I'm a bit out of practice ...

You beat me to it. That's what I'd have said, too. Without getting my hands on it (and possibly a polarising microscope) it's almost impossible to say.

Also I did a bit of geology but I'm really an oceanographer, so I'm no expert.

I've seen similarly shaped pebbles on the raised beaches on Jura, though.

Sam

 

[Globalti]

Maybe I didn't explain clearly enough; what fascinates me about this rock is that it appears to have imperfections running through it that arrived through different means and at different times in the life of the rock, the later actually cutting across the earlier.

 

[snailracer]

Dinosaur egg, fossilized.

 

[661-Pete]

[Spock]There's life there, Captain, but not as we know it[/Spock]

 

[theclaud]

Mipancertite, I think, but I'm no expert.