In Tolkien's legendarium Fëanorian lamp appears mainly in the story Of Tuor and his coming to Gondolin. It is described as a lamp that gave blue radiance from a flame trapped within a white crystal. These lamps were made in Valinor and the light from these lamps can not be quenched by wind or water. Even though Noldor were famous for these lamps, their secret was lost to them. Gelmir of Finarfin's people had one of these lamps in his possession at his meeting with Tuor.
Another instance when this lamp make an appearance in Tolkien's writings is in the story of Narn i Chîn Húrin where Gwindor, an elf who escaped from Angband had possession of this Noldorin lamp. When Beleg Cúthalion was slain by Túrin, it was from the light of this lamp that Turin was revealed that he had slain his friend Beleg. But in the published version of Silmarillion there is no occurrence of Fëanorian lamps.
- Fëanorian lamp at Wikipedia