I went Sunday. The Huntsville Gem and Mineral Society had a museum-like display along one wall, a 'flume' for 'panning', and lots of sellers. I liked seeing the local 'Paint Rock' agates.
Huntsville Gem and Mineral Society
The GMS makes day trips to collect rocks. Good for kids.
BTW - there are several regional gold, gem, and mineral mines open to tourists (most are good for kids). Franklin North Carolina (east of Chattanooga, north of Atlanta) seems to be the epicenter of Southeast mining. Supposedly there is gold in Chilton County and east - central Alabama.
Franklin, NC; Mountain Treasures. Simple Pleasures