*sees the perfect opportunities to pull pranks on Bob*
Hey, Sherpas ... pssst ! com'ere ... *whispers in Sherpas ears*
Go get some handfuls of dirt, put them in a pan, and go tell Bob you found a bunch of gold. Then, tell him to look at what you found, and *believe* me, he will think the dirt is gold. Tell him that if he isn't sure, to bite it in order to test it out (I've seen them do that in movies, don't worry, that's a real thing, Sherpas).