Something that is indeed much more complicated than simply 'magic with crystals'. Crystal work is, in fact, one of the areas i specialize in, since my talents lie towards energy work and crystal magic is purely energy. "crystal magic" is the art of tapping and utilizing energy innate in stones and using it for an end, although they are also frequently used in spellcasting as well. Every stone has its own innate enery and 'personality' and symbolism. some examples:

hematite-healing, soothing, peaceful. properties--receptive, lunar.
quartz-the "universal crystal" in its pure form, it can acquire the properties of almost anything else.
rose quartz--peace, love. properties--receptive
citrine--power, energy, fire. properties--projective, sun.
bismuth--higher planes, the spiritual realm, astral projection. properties--receptive/projective, neutral alignment.
amethyst--spirit, energy, psychism, dream ehancement. properties--receptive, lunar.
sunstone--raw power and symbolism of the sun. properties--projective, sun.

These are just some examples. each stone has its own meaning and usage.