Pearls have often been used to enhance cameo jewellery and other items. For thousands of years, seawater pearls were retrieved by divers in the Indian Ocean in areas such as the Persian Gulf, the Red Sea and the Gulf of Mannar. Evidence also suggest a prehistoric origin to pearl diving in these regions. Starting in the Han Dynasty (206 BC–220 AD), the Chinese hunted extensively for seawater pearls in the South China Sea. In the 14th-century Arabian Sea, the traveller Ibn Battuta provided the earliest known description of pearl diving by means of attaching a cord to the diver’s waist. Reference: Wikipedia
Below are some examples of pearls used with cameos.