Yes thaqt necklace was from the real titanic it is call the heart of the ocean. im not sure however if they used the real necklace in the movie or a prop. the real neclace is in a measuem i have personaly seen it and it is amazing. check it out.
Sadly, the necklace never existed; it is a made-up myth. Its legend is borrowed from the story of the Hope Diamond, a large blue diamond once owned by Louis XIV of France.