Originally posted by jonnin:

the wishbone won't shut up until you destroy the chest or hit the vein once with a pick.
it needs to be beeping constantly to dig at your feet.
its really not too complicated. silver CAN be out of reach, but its rare.
the WB can find other things too, in the swamp and more.

For the silver vein it won't shut up until you mine out the center of the deposit. If you separate the entire deposit from the surrounding stone you can hit the center of the deposit a couple of times and the entire vein will shatter into a shower of stone and silver ore.