. I m o r t a l .
There live still those of whom Lúthien was the foremother, and it is said that her line shall never fail. Elrond of Rivendell is of that Kin. For of Beren and Lúthien was born Dior Thingol's heir; and of him Elwing the White whom Eärendil wedded, he that sailed his ship out of the mists of the world into the seas of heaven with the Silmaril upon his brow. And of Eärendil came the Kings of Númenor, that is Westernesse.

The Lord of the Rings pg.189-190

. E ä r e n d i l .
The mariner who sailed the Great Sea at the end of the First Age. He long sought a way to Aman, to seek the aid of the Valar against Morgoth, but the way was hidden. After the Sons of Fëanor attacked the Exiles of Gondolin seeking the Silmaril, Elwing his wife escaped and came to him at sea, through the power of Ulmo, in the shape of a white sea-bird bearing the Silmaril on her breast.

Through the power of the jewel, it is said, Eärendil was at last able to find a way to the Undying Lands, and there stood before the Valar and begged their aid in the wars against Morgoth. The Valar listened to his plea, and sent the great force that finally conquered the Dark Lord and freed Middle-earth.

Eärendil's father was a Man, and his mother an Elf, so he and his wife Elwing and their sons were given the choice of race to which they wished to belong. Elwing chose Elvenkind, and Eärendil did so too for her sake. He now sails the high airs with the Silmaril upon his brow, shining as the morning and evening star.

The Encyclopedia of Arda 'Eärendil the Mariner'

. S i l m a r i l .
A fabulous green gem made in Gondolin during the First Age. Stories of its creation differ in detail: some name Enerdhil as its maker, but Celebrimbor son of Curufin was more likely to have been the jewelsmith who created it. The Elessar had the light of the Sun trapped within it, and those who looked through it were said to see the withered or aged as whole and young again. It was even claimed to have some power of healing.

This Elessar was saved from the Fall of Gondolin by Idril, who gave it to her son Eärendil, and with Eärendil it was carried across the Sea to the Blessed Realm. In the Third Age, another Elessar was seen - the Elfstone given by Galadriel to Aragorn - and some said that this was Eärendil's jewel, brought back to Middle-earth by Mithrandir. In truth, though, Aragorn's Elessar seems to have been a new stone, also made by Celebrimbor, with less power than the original jewel.

The Encyclopedia of Arda 'Silmaril'