A solid material whose constituent atoms, molecules, or ions are arranged in an ordered pattern extending in all three spatial dimensions. If cut properly they can be used to enhance someone’s chi. Most of what people use crystals for is to convert chi into either mana or pishogue to make white or black magic easier, more efficient and less dangerous. Using crystals just to enhance chi wasn't something often practiced. Martial artists and psionics are the only ones that make actual use of chi as the main source of power. Psionics isn't something people teach much, hence the plethora of akiras, and martial artists for the most part haven't thought much of crystals, mostly perceiving them as fragile or cheating.