according to this
site the 559s are 100% cotton. i have a couple of pair that i'll check when i get home this evening to verify.
i noticed you're a fan of the carhartt hamilton pants, as am i. the rise and the fit in general of the 559 is pretty similar to the hamilton although, the legs of the 559s are a bit wider.
as for the pocket size, i don't think they're overly small but if that's a concern, i'd go for a 505 and go up a size.