Gem hunting is simply the act of going out and looking for interesting geologic finds. There are a few different types of gem hunting:
If you dig up your own rocks and dirt to find gems in, then you're a recreational miner. You might be allowed to excavate a disused area of a mine owned by someone else or get permission to quarry part of someone's property -- including, in some cases, government property. Panning or sluicing for gold, known as placer mining, is another form of recreational mining.
When a large-scale, commercial mining operation extracts minerals from the ground, it ends up with leftover gravel and dirt. It usually isn't worth the time for these groups to sort through leftovers in order to find small gems that they missed, so they just pile it in a place called a mine dump. Sometimes you can comb through mine dumps for free; other mines charge a fee to dig through their remnants. This is one form of a fee dig.
In addition to mine tailings, some mines prepare gravel and dirt deposits specifically so people can come and dig, looking for gems. Fee digs attract both tourists and gem hunters. Some mines even import rock and dirt from other regions so people may search for exotic gems normally not found in that area. Or, mines might provide material from deep underground, where the average gem hunter couldn't go. Fees can range from $50 to $100 or more, depending on the length of time you spend at the site. Essentially, you're leasing the mineral rights to whatever you find. However, some fee digs charge a percentage of the wholesale price of any rough gems you find.
Hunting for gems can be as simple as heading out into the wild and seeing what you can find on a walk. You won't be heading to a specific mine or looking through pre-dug piles of gravel -- you'll be searching for gems and minerals already at the surface, exposed by rock falls and erosion. You might do a little digging or chiseling, but no serious mining. You'll probably be hiking in a state park or on private land, where someone has given you permission
Now that you know the different types of gem hunting, let's examine the ideal gem-hunting grounds to meet your needs.