It's an old name, I'm not trying to introduce a new name, I didn't name it. It's been called a split pea soup to some collectors for a long time too. Can't help that you haven't heard of it. Congrats on your first post here.
Yeah, if it wasn't in the lot of MKs with similar colors and av (and I think all of them were dug), I might have had a hard time figuring it out, but still I can see MK in it. This one looks dug too.
I'm guessing it's some kind of soot from burn-off of contaminates or something like that in the tank. I melted a marble with an oxy-acetylene torch once and it changed the color and gave it that metallic look too. Impurities I guess.