Wow, interesting, also good description of the shape. Not something I'm familiar with being that dark! Are the dark marks above (or to the side) where other brackets have been dislodged? Did you notice the colour of the pores? You didn't get a photo of them by any chance?
Oh, I see it has loaded right way up! My bad, it appeared to be loading sideways on my iPhone.... I didn't notice the colour of the pores, nor take any other photos of it. Next time!