Well, what if you just ransom it? Targeting it is hardly destructive.
How do you threaten to destroy gold?
Oh, I dunno, maybe by promising to vaporize it with multiple thermonuclear warheads? I mean, I did contrast the idea with an a attack involving a hypothetical Dyson sphere...
I suppose if you manage to break into Fort Knox, you might have some nukes, too. Seems like not-the-simplest-plan.
It's not a bad idea. In fact, I found a how-to video.