This one detonated above ground, the other, GBU-57 a/b, is a penetrator, and bigger too...
This is the one I was thinking of: http://www.businessinsider.com/the-30000-pound-bomb-that-could-be-used-against-irans-nuclear-facilities-boggles-the-mind-2015-6
Seems like they could use it to take out North Korea’s underground nuke? Maybe that’s just wishful thinking. Stealth delivery would be a problem now that they know Trump isn’t afraid of blowing things up.