I don't know where you live, but there are also places that let you dig you prospect for jem stones and such for a small fee. You go out and either dig thru or sift thru looking for jem stones. Then you can have them cut it, polish it, and mount it for you. Not free but much cheaper than in the stores, and your quality is limited only by what you find.
There is one up north here, I wanna say UP Michigan area, that has a mine where you can prospect for some type of diamond. Apparently it isn't an actual diamond, but when cut and shined up sure looks and sparkles like one.
The lady that does this stuff is on the Travel Channel, interesting stuff.