What generates gems?

[Edi]

Thanks for mentioning that those gem producers are not listed, because they should be in the special column. It's been a LONG while since I added anything with an ID less than 1700 into the DB, so this sort of reports are good. I'm not infallible, so reports like this are the only way to get this sort of oversights noticed.

And as Endo said, exemplary performance right off the bat. Having the unit number means I can immediately find what I'm looking for.