This stunning sterling silver art deco ring features a round black onyx stone decorated with marcasiteblack onyx is a member of the chalcedony family and has been used in jewellery for centuries most notably in ancient cameo jewelleryonce used as a substitute for the shine of a diamond the natural semi precious gemstone marcasite is now celebrated for its lustre and metallic beautyblack onyx informationnumber of stones 1stone shape roundstone size 13mm x 13mmcarat weight 300ctnatural