I think the answer is no, but I would love to have a second opinion.
On Saturday, I fell while crossing a boulder field in the pouring rain. I was on my feet, and then I was on my back on a rock. Fortunately, my pack had a lot of extra clothing, plenty of freeze-dried food, my air mat, and lots of other stuff to cushion my fall, and I'm not even sore. But I'm 6'1", 250 pounds, and my axe was on the outside of my pack, the way yours probably travels when you don't expect to need it for the next several miles of trail. So it hit the rock directly, and my and the pack's weight came down on top of it.
There's no visible damage. I'm asking because Freedom of the Hills says you should retire a carabiner that's fallen from a cliff, it will have micro cracks and should not be trusted. An ice axe uses a lot more metal, so should be stronger, and it doesn't stand up to nearly as much force as a biner might, so I think it's ok. But, like I said, I'd love to hear from somebody who knows more than I do.
Ice axes are used to pound pins, torqued into cracks, employed as crowbars on loose rock when cleaning mixed routes, and all sorts of other high-impact stuff. I don't think falling on a rock with one is going to harm it much.
Micro fractures are more of a problem with fatigue (high cycle) loading, particularly with AL, which, unlike steel, has no theoretically infinite fatigue life. That's not to say other materials wont' fail spectacularly (Tacoma Narrows, baby) if the cyclic loading isn't properly characterized during design, or some modification later on doesn't screw up the works.
If you can see a fracture at all, of course, get rid of it. The sharp end of a fracture concentrates stress; the smaller the crack tip radius, the more the concentration. The area of maximum stress on a biner is at the surface, so any visible crack has the potential of propagating inward until the cross sectional area is too small to bear the load and it snaps all of a sudden like. larger radius divots are usually less of a problem unless they're so big that the metal has been work hardened (made more brittle) due to the impact.
Personally, I'd use nuts thrown off El Cap - small moment arm on that loading and the alloys are more ductile, but not biners. I'd probably use the cams, too, cuz I'm that much of a cheapskate.
Edited by tvashtarkatena (10/15/1211:30 AM)
All things to all people, all the time.
So if there is visible damage, how bad does it need to be to replace the ice axe? I once used the shaft of my camp corsa nano to pound in a picket. I didn't know the better method of pounding in pickets at the time (holding the axe vertically). Those are small dents in the shaft. Do you think I did enough damage to my $150 axe to warrant replacement?
Science is the belief in the ignorance of experts. -Richard Feynman
I agree with Tvash. Fatigue can be an issue with aluminum (check out airplane failures) but your ice axe should be fine. Gear failures are rarely due to hardware but software, and I'm not talking about your computer.
Nuts thrown off El Cap I would use but not cams.
Personally, I am allergic to snow and ice but like to snuggle with rock.
I do what I want and take what I get