[meteorite-list] rough/"bubbly" fusion crust?

[Darren Garrison]

I have a small individual where the texture of the fusion crust is completely different from any of
the others in my (admittedly small) collection.  On the rounded side, it is of typical smoothness,
but on the flat side, it feels almost like fine sandpaper and appears almost porus.  Is this more
likely to be a post-fall erosion feature, or some sort of "bubbling"/"frothing" of the molten rock
during ablation?

http://webpages.charter.net/garrison6328/nwa869_rough_b.jpg
http://webpages.charter.net/garrison6328/nwa869_rough_a.jpg