This is one of those colors that lurks in your stash, waiting to be rediscovered. The reason that it is particularly effective at lurking is that it looks like rods of black. And you think - oh, a stash of black (if you have lost the label) - and then you use it, and blammo - not black.
Which may or may not mess you up.
You see the green as it cools when you are working it - so it doesn't come out of the kiln a complete surprise. The rods might be all black, or they may have some green streaks. It is a creamy, soft color to work - which is your first indication that you do not have a black on your hands.
It is, apparently, a copper-laden green - judging from the red patches of reduction that can form accidentally if you are not working in a balanced flame.
Fun, eh? Lovely little color, this one.