It's not
H. asinina. In fact, I can tell you a lot of species that it's NOT, but it's hard for me to put a name on it. It has the shape and sculpture of
H. varia, but I've never seen a black one.
H. dissona can look like that, but it has a very limited range (mostly Tonga) and is considered rare. Same goes for
H. fatui.
H. dohrniana is somewhat more common, but it would be a rare find under normal circumstances, and I've never seen a black example of that, either. Where are you located, and do you know where it supposedly originated? If you're in Australia, all bets are off
You can try to match it to one of the species here. Note the sculpture, how elongated the shell is, and how many holes are unfilled:
http://www.gastropods.com/Taxon_pages/TN_Family_HALIOTIDAE.shtml
The most likely common candidate is probably
Haliotis varia, even though it would be an odd specimen.
Cheers,
Don