Sea salt and anti-caking agents
Funny enough, I just checked my sea salt. It also has an anti-caking agent. But mine is calcium silicate. Wiki doesn't even have a section for it's use in food products. It's used as a "safe alternative toasbestos".
I think I got mine from Whole Foods. So just be careful when you buy Sea Salt. Even a store, such as whole foods, who claim to pride themselves on being natural, don't really care about your health.
That's why they make such a big deal about selling Agave as a honey substitute. Agave is one of the worlds most harmful food products to put in your body