onyx

Onyx is an oxide mineral with a trigonal crystal structure. The name ‘Onyx’ comes directly from Latin word of the same spelling meaning ‘claw’ or ‘fingernail’. This name stems from the flesh-coloured parallel bands of layered chalcedony that form onyx and resemble fingernails. Although traditionally onyx refers to the black variety, there are other shades. Sardonyx, for example, refers to red or yellow coloured onyx that have been used in jewellery since classical antiquity. Yellow onyx has also been used in lavish interiors. A sumptuous example is a carved Napoleon III bathtub designed by Donnadieu for the Hotel de la Paiva, Paris.

Pliny the Elder describes in his natural history, techniques practiced to enhance the natural colour of onyx by soaking and boiling in sugar solutions before treating the stone with acids (sulfuric or hydrochloric) to carbonise the sugars into the upper layers of stone. 

 Onyx has a hardness rating of 6.5-7 on the Mohs Scale making it fairly resilient to wear in jewellery, but makes it fairly easy to carve into beads or cut into flat sheets to form geometric shapes. Because of it’s deep black colour Onyx has historically been used in mourning jewellery, such as rings to remember the dead. In the Art Deco period (1920-30s) of European jewellery, Onyx became a fashionable stone, used to create dramatic colour contrasts when placed next to rock crystal, emeralds or diamonds. 

 The main source of Onyx has been India. The shiny surface of onyx, when polished, closely resembles that of lacquer, which led the stone to be included in intricate ‘Oriental’ style cigarette boxes or art deco jewellery.