Not sure on the exact cap, but got skillups on these + wind crystal at 48 Goldsmithing. Thanks, SE, for adding a way for us to level Goldsmithing sub like a cheap ***.
The cap on these is 51. I started skilling on them with Advanced support at 40, which is a bit extreme, but I had amassed over 50 of them. Best to sell any other geodes to buy more of these.
