The Wishbone you get from Bonemass helps you find where Silver Ore is buried, it doesn't encourage it to start appearing in the Mountain Biomass. Unlike Copper spawning in a huge node or Iron appearing in Scrap Piles in dungeons, Silver is buried underground and in a long snake-like formation.

With that, once you've found and begin uncovering Silver, you can dig underneath and around it until you have it fully exposed (end to end), if you dig one of the edges the whole thing will break almost in one go. Be sure to bring a Cart or mark the location as you cannot use a portal to bring it back, same as all forms of Metal.