The Crown of Empress Eugenie was created in 1855 by Gabriel Lemonnier. Napoleon III finally chose not to be crowned, so Eugenie never wore this at a coronation.

The shape of the Empress's Crown, typical of previous representations of imperial crowns, was conceived following a pattern already found on the Imperial Arms of the First Empire. The arches are formed by eight eagles alternating with long laurel leaves. A globe topped with a cross surmounts the arches. The eagle and palmette motifs are recurrent imperial symbols. The Emperor's crown is thought to have had the same shape but it is now lost.

The eight eagle-shaped arches are made of chased gold, the others, in the form of palmettes, are composed of several diamonds with one larger diamond in the center. Each palmette is flanked with two emeralds. The arches join under a diamond globe set off with a circle and a half circle made of thirty-two emeralds and surmounted with a cross composed of six brilliants. A large part of the Crown diamonds were used for the Emperor's crown, while for the Empress's crown, they were employed in smaller numbers. The emeralds, on the other hand, were the property of the Emperor.

(information taken from the Louvre site. See link)