Lightsaber crystals, also known as kyber crystals, were a variety of crystals, gems, stones, or other objects that were used as the energy source of a lightsaber.
At the heart of every lightsaber was a set of crystals that resonated to produce the efficient, powerful blade. While the most common crystals used in the process were from the Adega system, Ilum, and Dantooine (in the so-called Crystal Cave), Jedi and Sith used a variety of crystals to produce various colors, effects and unique abilities. Some crystals could even enhance the Force skills of a particular user. Other gems, such as colored crystals or diamonds, were used exclusively for prismatic effects. However, not all lightsaber crystals were actually crystals. Plenty of Jedi or Sith used a different material or substance in place of a crystal, such as physical remains, shards of glass, and even special micro machinery.
During the Great Sith War epoch, many lightsabers were created using Kunda stones, a natural geologic formation from the planet Kadril, in place of crystals. These stones boasted numerous practical applications in medicine and communications; however, when added to other focusing crystals, they produced a broader beam.