Gold=>Gems shouldn't be possible! Really, money is so much more common than gems... Besides, 25 gp would be too little and by a big amount! It would be more economical to change fire gems to gold and from gold to astral pearl than to change them straight to the pearls... Even without any alchemy bonus! And even with a bigger number, it would be possible to get infinite number of gems... Even with a 50 gp per pearl, Wish would only cost you 5 000!
