[Evilhomer]

You don't alchemise as a rule. A better option is to use wish and turn your astral gems into x2 other gems. A reasonable good position can turn out 75 clams by the turn of say 60-75. If you use those gems to cast wish(gems) each turn you have basically increased your gem income with 150 gems. That will probably double your ordinary gem income - not to shabby!