My husbands birthday cake is based off his favorite computer game... Starcraft. In the game you mine for "minerals" and I'd like these to be as "realistic" as possible but not made out of fondant. I've attached a picture. My initial "brilliant" idea was to make rock candy. However, it's been a week and the sugar crystals are still so tiny that it's just not going to be right. Now I'm thinking of using isomalt but am guessing i'll have to do it by hand. This is the first cake i've done using techniques not shown to me by somebody else and I definitely need practice. I'm worried they won't come out just right. Does anybody have any ideas of the best way to get this shape/look? I also only have two days to do it. Any advice is greatly appreciated!

I feel like they sell a silicone mold kit at the craft stores. Could you make a mold using a real crystal shape and use a hard candy recipe? Just a thought.