Cameos so popular for their pleasing colours.
They are found set in rings, brooches, pendants and the like, and were originally created from gemstones with different colours in their makeup, such as sardonyx and cornelian.
Sardonyx is from the onyx family, which in turn is a variety of chalcedony demonstrating straight layers of parallel, black and white pigments, which can prove very dramatic and ideal for cameos.
Practically all onyx jewellery has been dyed to improve colour density, with some coloured blue, red and green to match a particular suite.
Being extremely porous, sardonyx is found in wonderfully warm, earthy colours with evenly spaced lines of sard in all shades of brown and, in some instances, a bright orange red. Being so distinct, it is also carved intaglio, ie the reverse of a relief carving of a cameo, and used as a seal and set in rings or seals.
A famous, medieval jewel that was quite possibly a brooch is the Schaffhausen onyx, dated to the mid 13th century Germany and now in the Museum zu Allerheiligen, Schaffhausen, Switzerland.
Just 5in (12.5cm) across, this superb piece set with gems in a gold frame with a repoussA and cast decoration, features cameo figures on the front and back.
Trendy themes continued to be Greek gods and a superb gold and shell cameo necklace and earring set depicting scenes of Apollo driving a chariot with Cupid and Psyche within beaded frames is typical of this populist style.
This particular set sold in Bonhams for pounds 3,800 recently, cased in a box by Carrington & Co of Regent Street.
For all antiques and works of art advice, Jeffery Muse is always available on 029 2072 7980.