It is really pretty, is what it is. 
You probably won't hurt it by cleaning it a bit more. It is a cryptocrystalline quartz.

Yes, that's a very nice and large vug for that Savannah River material.
And, as Rebecca and John have already said, a real pretty
blue on the botryoidal chalcedony druse.
I would first have to look closer, with a loupe, at all the
dark spots to make sure they are just dirt before washing
them away. Then take a wet toothbrush and try a little area
before going at the whole piece. There can be a lot of
interesting accessory minerals found in those vugs.

Toward the bottom of this link they have a list of some of
the accessory minerals you can find. (Even tho I think they
have mis-spelled chalcedony in their list. )
http://www.aikengmfs.org/PowerPoints/2012AGMF_Girard_Chert.pdf

Thanks for the pic,
Joe

Good enough, Peter. Thanks for the picture.
Since chalcedony is a form of cryptocrystalline quartz it is not too much of a
stretch to see the two different forms next to each other
on the same piece.
Here's another link for you from the "Quartz Page";
http://www.quartzpage.de/chalcedony.html