a single generator crystal has six facets meeting equally in a sharp point.  Large or small, this crystal is the optimum shape for generating energy.  It optimizes healing energy and aids focus and clarity of intention.  A generator cluster is very large with many long points, each can be programmed for a specific purpose.  This crystal brings group together in peaceful harmony - each person can have a point programmed specifically for them.  a generator cluster is extremely useful for generating healing energy and is often placed in the center of a healing group.