uhm, i have a world that i started a few months ago, where i live in a plains area, next to a desert and a desert village.
I have a really big mine that I work in below my home, (shaft mining or whatever its called), and down there, around layer 4-9, I have found about 7 emeralds. They have only come as one though, never a chunk of them, and that is the only world i have ever spotted emerald in
I found my first emerald when I was trading with a villager, never mined one. THREE signs for an EMERALD. Too bad I can't remember the seed. By the way, CreeperXassasin, did you honestly not know where they're found? Don't mean to be rude, LOL!