Safe to eat? cooked in Chinese cast iron (I think) wok

I mostly like the look and feel of my very lightweight Chinese cast iron wok (at least, I *think* it's cast iron), bought downstairs at Kam Man on Canal Street in Manhattan's Chinatown. But is it safe to eat what I cook in it? I thoroughly cleaned and cured it, but each time I take it down to use it, I am still drawing off, with dry paper towel or my dry fingers, a smudge of black sootiness. I've only used the thing four times. I seem to be shunning it. Should I?