Sorry it took my so long to respond, but I've had some trouble with the forum site. Anyway, it is true, the combination of stones does differ each game, you're best bet in general is to collect all the different kinds of gems, then save the game. If a stone gets fired, just restore your save game. It's cheap but it works. Also, I'd perfer it if we tried to move all talking off this post, no offense, but since it's posted as a simple q and a type thing, it sidetracks from the real point. Hope that all makes sense,
-Sean