You get a 2 minute cooldown on all mana gems when you use one. You cannot use multiple gems at once.
that macro will first use mana emerald then ruby, citrine.. so on
try to use multiple mana stones by pressing key in say.. 10 min fight. it will use mana emerald at first but after 2min when you press key again, it won't use mana ruby because autobar still recognises as mana emerald is existing until your fight is done.
this is why i want this macro to be fitted to stones bar so i can save 1 action slot