You're going to want to label this - otherwise - you're going to get it mixed in with your black.
Not that, if you are making solid, self-coloured beads, you'd actually be able to tell the difference!
This is a very dark transparent grey, slightly streaky. You can see from this test paddle, I had to squish part of it with tweezers to get it thin enough to show that it is a transparent. (The thin part is 2.4 mm, the thicker part, by the rod, is 4 mm.)
It looks somewhat brownish when hot.
Here - a spacer made with the Charcoal - it looks black!
The two flanking spacers are both solid Charcoal - the one on the left was reduced, with no apparent effect.
The Charcoal on white shows it's true nature - when melted very thin, it show a very nice, pure grey, with no overtones of blue, purple, or anything else.
Closer examination shows that there has been some separation in the white, and that the Charcoal bleeds into the white.
Not what I'd call a hugely useful colour - as I am not a fan of grey (the whole point of glass is the colour!) - but it's very nice to know it's there if you want it!