Marble King did not produce a true black color. What often appears black is really dark purple, and where that color thins out over white it definitely takes on a lighter purple color but not a purple like this one, IMO.
It seems to me that the prominent colors on this marble are green and purple, and there is some blue too. I think those dark colored streaks up in and near the top patch are where these colors come together in various ways to make dark or light browns depending on their "concentrations" or "thickness". In other words, I don't think the purple you see is coming out of those dark streaks like what you might see on a MK.