Note:  Do not rely on this information. It is very old.


Onyx, from a Greek 'word meaning a fingernail, referring to the contrasting bands of colour, is the name of that variety of agate in which the variously-coloured layers are evenly parallel and alternate white or grey with black. If one layer is brown sard or red carnelian, the stone is termed a sardonyx. Oriental onyx has long been exported from Broach and Cambay. The stone was until recently obtained from the Galgenberg, at Idar, in Rhenish Prussia, where it is still cut, polished, and artificially heightened in colour, though the raw material now comes from Uruguay. Onyx is chiefly employed for cameos and intaglios, as brooches, rings, etc. In ancient times banded varieties of stalagmite (q.v.), now known as onyx-marble, were also termed onyx.