Every type of crystal has a unique form, the way its molecules are laid out. Energy sent through a crystal will pick up this unique pattern. The effect of that patterned energy is debateable, but some people certainly seem to have positive reactions to some, and negative reactions to others. Quartz is highly unique. Its piezoelectric qualities are the reason it's used in electronics, but that unique effect carries over to psychic energies as well--it's a superb amplifier and focuser. (A diffuse energy beam sent through a crystal becomes more concentrated and narrower when it exits). This is the least debateable effect of any of the crystals.
--Winged Wolf
--Winged Wolf