Crystals that have grown together on a matrix (base). A cluster will fill a room with positive energy and is therefore very useful for clearing negative energies from the home & workplace. You may want to use one after an argument to calm the atmosphere. Amethyst or Smokey quartz clusters can be used to keep the spirit centred, as they have a certain property that keeps all the energy centres in the body aligned, balanced, and in harmony with each other. Clear quartz or amethyst cluster beds are excellent for cleansing other crystals, but ensure it is fully charged in sunlight for at least six hours beforehand! Then place your tumblestones or other regularly used crystals on the cluster bed for a few hours and they'll be full of energy when you next pick them up