[Xrystal]

I suspect, because I can't see anything else that would trap it in the events, that it is an interaction probably of type INTERACTION_HARVEST.

If it is then the only way to catch it is to test for it using the update routine like I did with my Gatherer addon.

I didn't come across any skyshards while I was testing it the other weekend so can't say for definite but it is my best guess.


Edit:
Although, EVENT_STATS_UPDATED sounds promising.