Gold and Micromosaic Pendant-Brooch/Necklace, the pendant by Ernesto Pierret, circa 1870

Decorated in multi-colored tesserae with a Greek cross within a quatrefoil panel, the gold frame and pendant loop accented with beadwork, the reverse with a glazed locket compartment, signed with monogram for Ernesto Pierret, suspended from a slightly sprung gold choker accented with twisted wire, length 15 inches. 

Examples of similar chains are illustrated in French Jewelry of the 19th Century, Henri Vever, translated by Katherine Purcell, p. 782.