Store your Crystals with others of like hardness. If you store your crystals such that they are touching each other, make sure they are of like hardness, otherwise you will have a very high chance of having your softer crystals scratched by harder ones.
Here is a list of the hardness of some popular Crystals within the Mohs Scale of Hardness:
2: Selenite, Desert Rose, Halite, Stibnite
3: Calcite, Celestite, Bornite (Peacock Ore), Septarian
5: Blue Apatite, Tektite, Charoite
6: Moonstone, Labradorite, Sunstone, Amazonite, Pyrite
7: Clear Quartz, Amethyst, Tiger’s Eye, Rose Quartz
8: Topaz, Emerald, Aquamarine
9: Ruby, Sapphire
German geologist and mineralogist Friedrich Mohs developed the Mohs scale of mineral hardness in 1812. It is based on determining which material is harder than another and therefore able to scratch it.
The list starts with the lower number being the softest and the higher number being the strongest.