The term "cameo" also refers to a proof coin that has frosted lettering and features, providing attractive contrast with the mirrored fields of the coin. The terms "deep cameo" and "ultra cameo" describe cameo coins having the boldest, most attractive contrast.
There are three main materials for Cameo carving; Shells or Agate (called a Hardstone cameo), and glass. Cameos can be produced by setting a carved relief, such as a portrait, onto a background of a contrasting colour. This is called an assembled cameo. Alternately, a cameo can be carved directly out of a material with integral layers or banding, such as (banded) agate or layered glass, where different layers have different colours. Sometimes dyes are used to enhance these colours.
Cameos are often worn as jewelry. Stone cameos of great artistry were made in Greece dating back as far as the 6th century BC. They were very popular in Ancient Rome, and one of the most famous stone cameos from this period is the Gemma Claudia made for the Emperor Claudius. The technique has since enjoyed periodic revivals, notably in the early Renaissance, and again in the 18th and 19th centuries. The Neoclassical revival began in France with Napoleon's support of the glyptic arts, and even his coronation crown was decorated with cameos. In Britain, this revival first occurred during King George III's reign, and his granddaughter, Queen Victoria, was a major proponent of the cameo trend, to the extent that they would become mass produced by the second half of the 19th century. The visual art form of the cameo has even inspired at least one writer of more recent times, the 19th-century Russian poet Lev Mey, who composed a cycle of six poems entitled Камеи (Cameos, 1861), as reflections on each of the Roman rulers from Julius Caesar to Nero. In 1852 Théophile Gautier titled a collection of his highly polished, lapidary poems Emaux et Camées (Enamels and Cameos).
During the Roman period the cameo technique was used on artificial glass blanks, in imitation of objects being produced in agate or sardonyx. These glass cameos were produced in two periods; between around 25 BCE and 50/60 CE, and in the later Empire around the mid-third and mid-fourth century. Roman glass cameos are rare objects, with only around two hundred fragments and sixteen complete pieces known, only one of which dates from the later period. During the early period they usually consisted of a blue glass base with a white overlying layer, but those made during the later period usually have a colourless background covered with a translucent coloured layer. Blanks could be produced by fusing two separately cast sheets of glass, or by dipping the base glass into a crucible of molten overlay glass during blowing. The most famous example of a cameo from the early period is the Portland Vase.
The earliest known use of shell for cameo carving was during the Renaissance, in the 15th and 16th centuries. Before that time, cameos were carved from hardstone. The Renaissance cameos are typically white on a grayish background and were carved from the shell of a mussel or cowry, the latter a tropical mollusk.
In the mid 18th century, explorations revealed new shell varieties. Helmet shells (Cassis tuberosa) from the West Indies and queen conch shells (Strombus gigas) from the Bahamas arrived in Europe. This sparked a big increase in the number of cameos carved from shells.
After 1850, demand for cameos grew as they became popular souvenirs of the grand tour among the middle class.
Conch shells carve very well, but their color fades over time. Modern sources for the best quality conch shell are Madagascar and South Africa.
Gemma Claudia Cameo – Roman, 49 A.D. Five-layered onyx Herophiloska Cameo – Roman, 14 to 37 AD This portrait of a man with laurel wreath is probably of Emperor Tiberius. The work is signed "Herophilos Dioskourid[ou] ("Herophilus, son of Dioscorides). The colour of the glass was intended by the artist to imitate turquoise.
Agrippina the Elder Cameo-Carved in Italy in the period of 37 – 41 AD. The carving is a three layer agate.
Ptolemaic double cameo-Hellenistic, 278–270/269 B. C. Eleven-layered onyx;
"Blacas Cameo"-Roman, about AD 14–20. This was carved from a three layered sardonyx. It is a fragment of a larger portrait of the Roman emperor-Augustus.
"Gonzaga Cameo" Ptolemy II and Arsinoë II. Sardonyx. 3rd century B.C.
"The head of Flora Cameo" – Benedetto Pistrucci. AD 1812 In this cameo the top red-brown layer has been carved into roses. The face is carved from the white layer. The collector Richard Payne Knight purchased the Flora cameo from an Italian dealer, believing it to be Roman. The Italian carver Pistrucci claimed to have carved it himself. Payne challenged Pistrucci to carve a copy to prove his claim. The ensuing publicity earned Pistrucci several commissions.
There are very few people working in this field as this is one of the hardest challenges for any gemstone carver. The combination of a highly developed artistic ability, craft skill and many years of experience are needed to be able to create life-like portraits.
It is quite rare, these days, for subjects other than portraits to be carved by hand as agate cameos. The traditional themes of classical scenes from mythology or a standard image of a young lady, are more likely to be made with the help of the ultrasonic carving machine as a limited collection of typically 50 – 200 pieces.
Today the most popular shells for carving are the bull mouth carnelian shell, Cassis rufa, from the East African coast; this has white and orange or white and brownish-orange layers. The most highly prized shell for carving is the emperor helmet shell, Cassis madagascariensis. This shell has white and dark brown layers and is known as sardonyx shell, and looks similar to the layered agate known as sardonyx.
The world center for cameo carving in shell is Torre del Greco, Italy. The shells are first marked with a series of ovals in a process called signing, then cut into oval blanks for the cameo carver. The actual cameo is mainly cut with a metal scraping tool called a bulino, an invention of Jewish artisan Antonio Cimeniello. A number of metal gravers are used: flat-faced, round and three-cornered. To speed production, grinding wheels are used to quickly remove excess material. When the details are completed, the shell is then soaked in olive oil, cleaned with soap and water and selectively polished with a hand brush.