It doesn't matter. Crystals are like containers to hold energy, and to release it. Different kinds of crystals emit different kinds of energy. But having them in the same place shouldn't mess with the quality of them or their ability to hold energy.
I'm going to be going down to Corpus Christi, Texas hopefully in the next few weeks to get our things out of storage. While there I will go to Casa Del Oro where they have all types of crystals. I'm taking a list with me of the kind of stones.