Missouri meerschaum all the way. I'll personally attest to their toughness: Last october I forgot my (relatively new) washington in the breast-pocket of a coat I stuck into the wash... for 1 1/2 hours on super-hot. Freaked out once I realized where it went.
That killed the shank, stripped the cake, the bowl's finish, and fissured its exterior in spots, yet its integrity remained unaffected. Thus I dried the bowl, sanded it smooth to 2000-grit, re-varnished that, replaced the shank and gave it a go...
My discovery was a pipe indistinguishable in all qualities from prior to the accident.
Who the hell says corncobs are throwaways?