CABOCHON
A stone which has been shaped and polished without faceting, the word
cabochon, sometimes shortened to ‘cab’, derives from the French word caboche
meaning dome or knob. Before faceting began in the late 13th century, most
gemstones were turned into cabochons. Certain stones are better as cabochons
than faceted stones – for example, if the stone has a particular optical features –
chatoyancy (cats eye), asterism (stars), iridescence, adularescnence. Lower
quality precious stones (including some sapphires, rubies and garnets) are
sometimes shaped into cabochons where the clarity is not good enough for
faceting, as are softer stones, since scratches are not so visible on a rounded stone.