what do the different skills DO?

[Kaputnika]

i don't understand yet what the dual- and pure-gem- mastery-skills do, and some other skills aren't very clear either. can somebody help me?

and the ctrl-key for several gems to choose from doesn't work on my mac.. does somebody know how to use that option on a mac??

thanx guys

[fractalman]

dual gem mastery: makes dual gems stronger. weak in gemcraft 1, strong in chapter 0
pure gem mastery: makes pure gems stronger. strong in gemcraft 1, weaker in chapter 0.
x grade gem masteries: give you starting gems. max out high grade when you get it.
armor: reduce banishment costs a bit.
gem bomb skill: makes the gem bombs more powerfull.