What also helped keep Coulterville alive was the fact that the town itself happened to be sitting on top of one of the richest veins in the Mother Lode. The ledge itself was three hundred feet wide.

Gold on the bedrock is a good rule of thumb, but not one that is 100 percent effective. There are plenty of exceptions. So, how does a prospector recognize those exceptions?

I recently had the opportunity to spend a day exploring around Butte, Montana and was amazed by the amount of mining that has taken place there. The old-timers called Butte “the richest hill on earth” and had pretty good reasons for doing so.

It is not necessary to have a PhD in geology, but you need to know the basics, so that’s what I am going to try to dig into here—the understandable basics of these gigantic gold deposits.