Micromosaic brooch with the Lamb of God, made by the firm of Castellani

The brooch is made of glass and gold mosaic, set in enamelled gold. The central medallion is made up of minute cubes of glass, or tesserae, of differing shades of colours. The halo of the Lamb (symbolizing Jesus Christ) is made of real gold tesserae, not glass. The outer border is decorated with enamel set within a pattern of gold cells. As the enamel does not fill the entire depth of the cells, the pattern stands out in relief.Pio Fortunato Castellani (1794-1865) pioneered the revival of jewellery techniques from the ancient world. His firm, carried on by his sons Alessandro (1823-83) and Augusto (1829-1914), became the most original and prolific producer of jewellery in the 'archaeological' style, so called because most of their work was based on actual Etruscan, Greek or Roman jewellery. This followed the excavation of Etruscan tombs in the area around Rome in the 1830s.The Castellani family themselves built up a distinguished collection of ancient jewellery, used as inspiration for their work. The border of the brooch very closely follows that of an eighth-century brooch from southern Italy in the Castellani Collection, which the family sold to The British Museum in 1865. Miniature glass mosaics have been made in Rome since the 1770s, but the Castellani firm were the first to combine 'archaeological' jewels with mosaics from the Early Christian and Byzantine churches of Rome: the design of the Lamb is based on the large-scale mosaic in the apse of the Church of Saints Cosmas and Damian in Rome.