Lambent was a type of crystal harvested by the Yuuzhan Vong.
Lambents were the fruits of a certain Yuuzhan Vong plant. Lambent fields gave fruit when they were located on the surface of a planet or in a gravitational field created by dovin basals. Lambent plants did not give fruit when placed in an artificial gravity well, such as interdiction fields existing on starships or space stations.
When ready for harvesting, the lambent would be cut from a milky sac hidden behind the leaves of the plant that grew it. Before cutting off the lambent, the harvester—or his helper, usually a non-Yuuzhan Vong slave—would have to calm the plant by touching it in a slow manner. Lambents were used as communication crystals or light sources, as they could be dimmed or brightened by the thoughts of whoever possessed them. They also can be used to sense or pre-sense hidden enemies.
At some point prior to the Yuuzhan Vong War, advance scouts of the Yuuzhan Vong were known to had seeded the planet Shramar with both lambents and muur with the intention of harvesting them at a later date. Nina Galfridian would reveal to Admiral Bylsma that the destruction of the lambents would deprive the Yuuzhan Vong of components for their biotechnology whilst the muur would be the loss of a food source for their forces during the Battle of Shramar. Anakin Solo encountered lambent-bearing plants on a field on Yavin 4 while in Yuuzhan Vong captivity. Solo used a personally-harvested lambent as a lightsaber crystal for his lightsaber. Because he became "attached" to his lambent, he was able to use the crystal as a conduit to vaguely sense any Yuuzhan Vong around him.
After the Battle of Coruscant, the beaten New Republic forces on Borleias supplied false information to the Yuuzhan Vong that stated they were growing lambents to equip more members of the New Jedi Order with the creatures to attune themselves to the enemy. Furthermore, the misinformation stated that lambents were being grown by the New Republic to power superlasers. Later, on the transformed Coruscant, the dhuryam World Brain began causing a number of incidents to the various biots on the newly crowned Yuuzhan'tar. This included the overheating of a lambent field which caused them to explode and catch on fire.
In 137 ABY, Master Shaper Nei Rin gave Cade Skywalker his father's lightsaber, which contained a lambent crystal of her shaping.