Crystal digging is in Mount Ida. Mount Ida is the quartz crystal digging capital of the world.
Diamond and crystal mining is in Murfreesboro.
It's a big open field and you pay to enter and keep what you find. You can get your finds appraised and many find diamonds without knowing they are diamonds.
http://www.craterofdiamondsstatepark.com/ for diamonds
http://www.mtidarvpark.com/ very safe and pretty place to stay in Mount Ida to go crystal digging.
It will be hot in Sept here and don't forget bug spray, wide brim hat, and good walking shoes.