Did that, in 1962 or 63. Started out as a fluke. I found a pretty rock, maybe five pounds, a mixture of milky and clear quartz, while on a hunting trip. I did notice that there was a whole shelf of it on the side of a cliff, above where I found it. Took it home and sat it on my desk, as a paperweight.
An aquaintance noticed it, and offered a pretty good price for it. Wanted it for his acquarium. I sold it, then and there, after warning him that I knew where there were tons of it. He told me aquarium stores would buy it from me.
Went back to the cite and dug up a few hundred pounds of it. The trunk of the car was so heavy it was nearly dragging. Sold enough of it over a few weeks to pay the cost and then some. Not profitable, however, as compared to any regular unskilled job.
However, found out that the pretty little veins that ran through it were GOLD!! Went after the gold, and discovered some Jasper Agate, in the process. Getting the Jasper was harder than getting the quartz. Getting the GOLD was less profitable than either of the rocks.
Most money I ever made on that, kinda fun to do, was panning gold out of a stream and selling it to passers by for whatever they would pay. $5.00 for a gold sample in a test tube and a gold pan was pretty easy to do. Pick a stream close to a road side rest stop or near a camp site. Business fairly good, all day long. Most streams west of the Rockies have gold dust in them that you can pan up out of just about any stream side or stream bottom sand. Now and then you will find a small nugget that you can pick up with tweazers. A nugget worth 50 cents will go for several dollars!
Or, you could go to Knotts Berry Farm, and pan it up cheaper and easier and still have as much fun. Then you are paying the $5.00 for the 50 cent nugget.
As long as I did it for fun, it was fun. The rest went down hill, and I'd just as soon forget it.
I would start off with a prospecting book, for rocks or precious metal, and then go to a gold pan. I still have several pans, and usually take one along. When I find gold, I grin, show it off to whomever is there, and dump it back into the stream where I found it. I don't even take it home.
I have met a few who make fairly decent money at this. Takes a huge investment, these days, as you have to handle high volume. Never met anyone successful - making a living - who seemed to be enjoying the life. High risk for clinically significant Paranoia - AKA - Gold Fever - from my experience. The more successful - the worse the symptoms!
Rocks, semi-precious stones, precious metals - good hobbies - not a really good business. YMMV
Ray D.