After extracting crystals from a sparkle, they will never grow back. The issue is in the aiStep() function of the Sparkle.java class, at line 286 and 287.

Although it checks for the sparkle's current crystal type to see if its CrystalType.NONE, it just sets its variant to that same type it checked against, which will always be CrystalType.NONE. It should probably be using the getRandomType() function located after that.