Was the Heart of the Ocean (Coeur de la Mer) a real diamond?

Titanic Heart Of The Ocean

No. The Heart of the Ocean diamond is a fictional device that James Cameron added to the plot in order to give Brock Lovett (Bill Paxton) a reason to hear Rose's story. The Heart of the Ocean is based on the famous Hope Diamond that King Louis XVI of France gave to Marie Antoinette to add to her jewelry collection
.

The Hope Diamond is currently on display at the Smithsonian Natural History Museum in Washington, D.C. It holds no place in Titanic history. As a result of moviegoer fantasies surrounding the fictional Heart of the Ocean, the Asprey & Garrard jewelry company decided to make a real Heart of the Ocean diamond necklace.

The 170-carat sapphire, surrounded by sixty-five 30-carat diamonds, was worn by Celine Dion during her performance of "My Heart Will Go On" at the 1998 Academy Awards Ceremony. The necklace later sold at a benefit auction for $2.2 million.