Large crystals can be used as generator crystals, in particular, quartz crystals. I am a long time owner of a large quartz crystal weighing more than a kilo, about 30 cm high, and 10 cm wide (1 foot high and 4 inches wide). This crystal is really intense, and if I sleep with it by my side, I almost always end up not sleeping – such is its vibrational field.
Quartz crystals like these have long existed and been in use by the ancient civilizations of yore. Their main purpose is to act as power sources to activate other crystals in linked layouts that are usually used for healing or meditation purposes.
Nobody really knows how large quartz crystals can grow. Large specimens weighing several tons or more and measuring a few meters high are not uncommon. In fact, most mountains in the world can also be considered as giant quartz crystals. This page lists down a unique ridge in Namibia, composed of very large, opaque quartz crystals which are not so obvious from afar.
Meditating with these large quartz crystals is dynamite. They are capable of emitting strong energy; therefore they need to be used with care. If you want to program them, make sure your program is only for the greater good of all and is positive in nature. Otherwise, the program will backfire on you, probably resulting in disaster.
I have used this large crystal to help realize a personal dream of conserving a natural area that was special in many ways, and every day I would instill a program in it to realize that goal. And guess what, several universities launched expeditions into the area and succeeded in getting the state government to declare the area a park about a year later! What I just mean to say here is that these large crystals are powerful, so your intent needs to be really right when you program them.
More often than not, large quartz crystals are used in group meditations for world peace. A group may sit in a circle and project their thoughts onto the crystal which it is believed, will then beam the collective energy into the universe.
If you own one of these large quartz crystals, you should place smaller crystals in a circular pattern around these “generator” crystals. This sort of arrangement provides for a constant energy flow, and helps to keep each crystal in the grid fully energized.