The name comes from the Greek word onux , which means fingernail. According to Roman Mythology, Cupid cut the divine fingernails of Venus with an arrowhead while she was sleeping. The fates turned the clippings into stone so that no part of the goddess would ever perish. Black isn't normally the color one associates with fingernails, but in Greek times, almost all colors of chalcedony from fingernail white to dark brown and black were called onyx. Later, the Romans narrowed the term to refer to black and dark brown colors only.
Even in Roman times, the black color of onyx was usually enhanced by man. More than 2000 years ago, Roman historian Pliny described a traditional technique for darkening onyx that is still in use today. The onyx is soaked in sugar water, then placed in strong acid. After boiling for two hours, the acid eats away the sugar and water, leaving pure black carbon. Today cobalt dye is also used.
Durable and easy to care for, onyx has a hardness of 7 and enviable toughness even when carved in intricate designs.