The French Blue was cut from the Tavernier Blue diamond on the order of Louis XIV of France. It eventually became the largest diamond in Louis XV’s Toison d’Or de la Parure de Couleur, or “Golden Fleece of the Colored Adornment”, constructed in 1749. In 1792, the Golden Fleece was stolen and broken up, and the French Blue never recovered. However, 20 years and two days after the robbery, the Hope diamond appeared on the scene. At the time of its disappearance, the French Blue was the world’s largest blue diamond. At the time of its appearance, the Hope was the world’s largest blue diamond. Many suspected one was cut from the other when the Hope appeared, but this was not definitely proven until 2010 by a team of experts (of which I was one, the effort is described at http://museumdiamonds.com/~scottsuc/index.php/french-blue.html. This resulted in a National Geographic program highlighting our efforts. An excerpt can be found here: https://www.youtube.com/watch?v=tjcasbTg36E.