I got 412 gems from one dugeon run with this perk. Well over 3/4 of all it was flawless and over 1/3 were diamonds. I for one like to collect these gems, I dont sell them. I like to make a huge mound of them in my house some where. I know the road to get this is long and annoying but its so worth it and you can get very rich off it.

what skill tree is this in?

Its not in a skill tree. You unlock it by finding all the stones of barenziah and the crown and give it to Vex at the thieves guild.

are those the unusual gems? there are like 10 total right

There are 24 of them...

Yes, that's those and sorry to say but no, there are 24 total but they are easy to find with the help of the wiki guide i found while searching google.

ah beat me to it

Love the perk as well. Brings in so much extra profit for those Dwemer ruins.

Just clearing all the dungeons and travelling everywhere to obtain all 24 are a blast, as well as the crown. I was hoping I could keep it for one of my display cases afterwards, but yeah, the reward is even better.