Sardonyx is a combination of the minerals sard and onyx, which together form the reddish-brown or orange stone with bands of white or black. Sardonyx was often used in Roman seals and signet ...

The original gem stone for August is sardonyx, which a combination of alternating layers of sard and onyx. It has a reddish zebra-striped hue with white or black bands running through it. ‘Sardonyx’ ...