Are questions about gold panning as a hobby or sport on-topic at The Great Outdoors?
The Great Outdoors Stack Exchange is for people who love outdoor activities, excursions, and outdoorsmanship.
- Outdoor activity: It's an activity and you have to do it outdoors
- Excursions: You have to go somewhere unusual (possibly even more or less into the wild) to do it
- Outdoorsmanship: If you look at it from an American perspective, it's even one of the most fundamental outdoorsmanship-things (just like hunting, fishing etc.)
There are even already questions on this site (or at least one :D).