I've been following this thread because in the area of Spain where i live, back in the 70's the first Ibiza exilated hippies came to establish a commune here which lasts to this day with over a 1000 people in peak times. I have been hearing several times about a strain that they "keep" called La Negra, meaning the black one, and they say it's a black coloured grass. I think i've asked to every hippie over fifty in the area, and of course got different stories, and even some seeds, which thinking they were very old i was going to try germinating after xmas, but in any case i put one the other day, and it sprouted in soil within three days, so, no way is what the guy told me. It was gifted, but that doesn't help.
Now, i've never seen it nor smoked it, despite the efforts, but one thing i've heard repeatedly is that La Negra, was Durban Poison, and this is from the more serious hippies i've talked to, who grew it back in the seventies and say it's lost now, maybe this adds to the probabilities.