In a pick up group, it should be split evenly unless some armor or something dropped, then the person who got said armor would be neglected from the split. Its fair in this regard that everyone who goes gets something out of it, and no one feels like they got worked over.
Its hard to say how people should manage their stuff though...a leader might say i put the effort of getting everyone together, im getting the alexandrites and your here for the armor (similar to how dynamis is) so its quite broad i guess.
edit: Or a leader might use those alexandrites to fund upgrades for peoples armor, which is which i assume if a market for those bloom thats what most would do with them
People who get 35 should not get Alexandrites. Everyone else split the total.
N = Total number of people who comment Rock.
R = Total number of rocks from the run.
P = Total people who didn't get the piece they commented (including those with alexandrite commented).
X = R / (N + 1)
Number of rocks that others (w/o comment) get = X / P
Number of rocks that people with comment get = X + X / P
Eg. If 1 person comments it, he gets 50% + his share of normal split from the other 50%.
There.. but I dare you to do it.
Edit to clarify: the reason I think others should still get some is because inherently, the guy commenting rocks gets an advantage as he's almost surely going to exit with something while those commenting a piece of gear are taking a gamble.
letting someone take all the alex would be the same as having a dynamis group all pay entry and 1 person taking all the coins, except it's AP this time and not gil.
helping out a friend is different, but this isnt the case in the op, right?