Easiest/Fastest way to gain ore/gems?

Is using Eiko's "Jewel" the only way? Are there any enemies in disk 4 guaranteed to have ore for stealing? Because I want to power up Garnet's eidolons and... using jewel it would take me HOURS... If so Id rather just get 99 ore for 50% Odin kill and keep all the gems I already got from chocobo hot and cold etc (which are quite a lot)

EDIT - I think Garudas are the best place after some searching.. Its a 3 in 1 for me actually.. Zidane steals phoenix pinions + ores + ethers (yes they have all that for stealing.. pretty awesome), gets Thievery pumped at the same time, eiko spams jewel to get ores, and after winning they also tend to drop an ore... So if youre looking for gems like me.. I doubt there is a faster way

For future reference:

before disk 4, if you hang out around the Outer Continent near the Qu's Marsh and Conde Petie, most of the enemies there drop ores or have them to steal- Zaghnols, Griffins, Goblin Mages, and you can steal ethers from Cactuars while utilizing the "Jewel" ability.

Also, finding the chocograph treasures early is a good idea as many of them contain quite a few of the jewels needed to boost summons.