i have all the trophies for this game except treasure hunter.  ive been farming long guis and shaolong guis for about 5 hours (in game time, not straight through) and all ive gotten was one platinum ingot, a dark matter, and a trapezohedron.  other than this strategy, the only one i know of is digging with the chocobo, but that doesnt seem like it will be too effective either.

EDIT: i do have the collectors and connoseiurs catalog equipped.

Unfortunately there isn't.  Platinum Ingot's the best way to go.

Long Gui farming is really worthless. They've got only 10% chance to drop Platinum Ingots, which is only twice the probability that the Adamantoises have of dropping one.

The best farming method is going to the final chapter, and constantly fight the Adamantoise near the save spot prior to entering the palace. You can beat him in under a minute with the correct strategy and you can get over 10 platinum ingots per hour, if you're lucky.

I farmed 20 platinum ingots in less than 4 hours there.

thanks, what is the best way to get there.  i just started playing the game again after taking a break since june so i dont really remember how to get to places.  

I think you can go back to the final chapter using the crystal in Vallis Media on Gran Pulse. You can either go to Orphan's Cradle or Eden, if memory serves me right. 

I haven't played the game since April last year, when I got my platinum, so my memory may be a little foggy there.

youtube it

Make sure you have Lightning in your party...

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