Thieves guild spoilers:
Wow. Finding the 24 barenziah stones gives the most overpowered reward of all time. It's a perk/active effect that gives more chance of finding gems in chests. What it doesn't you is that is massively increases the chance. Like, I'm finding flawless diamonds, sapphires and other things worth 500+ gold in literally every chest and urn, even if there's just 5 gold in them.
Nice! Are gems useful for anything other than selling? I have a bunch of them in my inventory and wondered if they were worth hanging onto.