Cameos have been carved since antiquity, and a true cameo is a hard stone on which a design is cut in relief. Usually the stone used had a two colour bands, a dark band and a lighter band, and the image was cut into the light band leaving the darker band as background.

These cameos were carved from semi precious stones such as agate, onyx and carnelian.

However this summary is concerned with cameos produced in the 18th and 19th centuries, mostly as brooches, and most of the 19th century cameos are carved from shell.

If the cameo is carved from a semi precious stone, and well described it will usually name the stone or include the word 'hardstone' in the description, and if that word is not present the cameo can assumed to be a shell cameo. Hardstone cameos sell at a premium to a similar shell cameo.

However cameos can be made from other materials including ivory, lava, plastics and glass, and some are made by setting a relief carving to a contrasting background which could more...be of a different material.

Cameos that are created by a mould rather than carving are considered faux or fake cameos, although they are collectable in their own right as costume jewellery. This includes cameos in materials such as porcelain, glass, resin, Bakelite, celluloid or other plastics.

After 1850 demand for cameos grew, as they became popular souvenirs of the Grand Tour among the middle class. Italy was an especially popular destination due to its prestigious history in mythology, the arts and culture. Most of the finest cameos came from there, and were often bought as souvenirs, or sent back home as a gift for loved ones. Popular subjects for cameos included classical groups, the classical heads or busts of maidens, youths or warriors, and mythological deities.

By the end of the 19th century the popularity of the cameo was waning. Though they were still being produced, the quality of the carving in many cameos became poor, with figures and portraits being much cruder than their life-like predecessors of the Georgian and Victorian period.

When valuing a cameo, many factors have to be taken into account, including the materials used for the cameo, the quality of the carving, the desirability of the subject matter and whether the subject matter is rare. The quality of material and workmanship of the mount is also important. Any damage to a cameo can affect its value.

The evaluation of a cameo should include an examination to reveal any cracks or breaks, and this can be ascertained by holding the cameo up to a strong light, and/or examining it with a magnifying glass or jewellers loupe.