I tick-mined (not flawlessly) for most of the hour and got 790 amethyst and 27 unidentified minerals.
The 790 amethyst comes out to about 5.3m xp (per hour), but this rate will vary quite a bit depending on how much effort and attention you put into it.
Note that this is including boosts from voting, gold members and the prospector's outfit. Semi-afk rates without boosts is around 1.5-2m xp/h.
