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Cameo is a method of carving, or an object such as an engraved gem, item of jewellery or vessel made in this manner. It nearly always features a raised (positive) relief image; contrast with intaglio, which has a negative image. Originally, and still in discussing historical work, cameo only referred to works where the relief image was of a contrasting colour to the background; this was achieved by carefully carving a piece of material with a flat plane where two contrasting colours met, removing all the first colour except for the image to leave a contrasting background.
Today the term may be used very loosely for objects with no colour contrast, and other, metaphorical, terms have developed, such as cameo appearance. This derives from another generalized meaning that has developed, the cameo as an image of a head in an oval frame in any medium, such as a photograph.
Many modern cameos are carved into layered agates. The layers are dyed to create strong color contrasts. The most usual colors used for two layer stones are white on black, white on blue, and white on red-brown. Three layer stones are sometimes made. The colors are usually black on white on black. The layers are translucent, this allows the artist to create shading effects by removing material to allow the background layer to show through. This way a very realistic, life-like quality to a figure can be achieved. For example thinning the top black layer on a three layer stone changes its color to shades of brown. Removing material from the white layer creates shades of blue or grey depending on the color of the base.
The hardness (Mohs scale) : 6.5 - 7.0
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