Silmiel, your confusion is understandable - the movie necklace "Evenstar" has nothing to do with the book. There have been some discussions on this topic; look at
Arwen's pendant, for example. Perhaps someone recalls other threads about it - I'll leave this one open for additional information.
__________________
'Mercy!' cried Gandalf. 'If the giving of information is to be the cure of your inquisitiveness, I shall spend all the rest of my days in answering you. What more do you want to know?' 'The whole history of Middle-earth..
.'