A precious stone, consisting of a mixture of chalcedony and cornelian, sometimes in strata, but at other times blended together. It is found,' first, striped with white and red strata, which may be cut in cameo as well as the onyx. Second; white, with red dentritical figures, much resembling the mocha-stone, excepting that the figures in the latter are of a black colour, instead of a red. There is no real difference, except in the circumstance of hardness, between the onyx, cornelian, chalcedony, sardonyx, and agate, notwithstanding the different names bestowed upon them. This stone was formerly much employed for the sculpture of cameos.