gems, beryl, emerald, glyptic, engraved gems, emerald bust of Nero, art market, Christie’s 1992

Common gem materials can present challenges in identification when fashioned into intricate carvings or altered by surface conditions. A miniature bust submitted to the East Coast lab—purported to depict the Roman Emperor at age 11–13 (circa 49–51 A.D.)—was examined for authenticity and composition. Due to the detailed carving, refractive index measurements were not possible, but hydrostatic testing gave a specific gravity of 2.70. Spectroscopy revealed weak chromium absorption typical of emerald, and a faint pink reaction under the Chelsea filter further supported this identification. The piece, semitransparent to translucent, displayed numerous fluid inclusions and small, unidentified crystals, one likely being biotite mica. Surface-reaching fissures exhibited yellowish brown iron staining, but no signs of oiling. Based on its properties, the bust was identified as natural emerald. If its reported provenance is genuine, it is probably Egyptian in origin. According to John Sinkankas, emeralds were mined in Egypt during the Graeco-Roman period through the 13th century A.D. Supporting this, Robert C. Kammerling of GIA collected samples from Egyptian mines in 1991 that matched the carving in color, transparency, inclusion patterns, and biotite presence.