Well, there's still nothing saying "the damage counts as magical" nor do you actually perform an Astral Combat attack. And as a mundane, you wouldn't like your AR of 0 + N/A = 0, anyway if it WERE an Astral Combat attack.
Sure you can punch the materialized earth spirit, at DV WIL/2. But you're vastly better off just not using the technique if it IS materialized. Presumably you'll do more damage w/o it.