Is this cast iron pan safe to cook in? My wife just bought this pan and I noticed this weird dark/black spot in the center with a bit of a swirl around it (never mind the brownish tint, this is due to my flax oil seasoning).
I don't care much about the looks, I'm just worried this might be unhealthy to cook in. Does anyone know what that might be?
From Johanna in the comments section:

In that case, regardless of if it's safe or mot, I would request a replacement from the store you bought if from. You're unlikely to get a smooth surface regardless of how much you season it and the seasoning will most likely just flake off around the swirl marks.

Turning the helpful comment given into an answer as comments are temporary.