Doesn't really fulfill any role and just makes balancing harder

just had this experience haha

Maybe adding the restriction that different crystal types only grow on certain (vanilla minecraft) blocks (like farmland for plants).
This could be a easy workaround I guess.
For example:
Pure Crystals only grow on Netherquartz blocks.
Ignis Crystals can only grow on magma blocks with lava source attached.
Aqua Crystals only grow on ice with watersource next to.
etc.