If you can't find unrefined, then by all means use refined - it will have to do! Definitely Sea Salt , NOT Epsom Salts .
I used Sea Salt until I found celtic Sea Salt , which is thick, coarse, and grey - definitely unrefined, and really delicious. You can find it at some health food stores - the raw store near me sells it, and probably online, too.
So yes to unrefined sea salt, yes to celtic sea salt, yes to refined sea salt if that's all you can get, no to epsom, no to table salt ;)