Onyx and sardonyx are varieties of agate in which the layers are in even planes of uniform thickness. This structure enables the stone to be used for engraving cameos. As is well known, these are so made that the base is of one color and the figure of another. This art of making cameos reached a high degree of perfection among the Romans and many superb examples of it have come down to us. The word onyx means a nail (finger nail) and refers to some fancied resemblance, perhaps in luster, to the human nail. Sardonyx is a particular variety of onyx in which one of the layers has the brown color of sard. Other kinds of onyx are those known as chalcedonyx and carnelionyx in reference to the color of the intervening layers. So-called Mexican onyx is composed of quite a different mineral from the onyx here considered, it being made up of calcite rather than quartz. Mexican onyx can be scratched easily with a knife while quartz onyx cannot. Mexican onyx has, however, the banded structure of quartz onyx and it is in allusion to this undoubtedly that the name has been applied. A sardonyx upon which Queen Elizabeth’s portrait was cut constituted the stone of the famous ring which she gave the Earl of Essex as a pledge of her friendship. It will be remembered that when the Earl was sentenced to death he sent this ring to his cousin, Lady Scroop, to deliver to Elizabeth. The messenger by mistake gave it to Lady Scroop’s sister, the Countess Nottingham, who being an enemy of the Earl’s did not deliver it to the Queen and the Earl was executed. On her deathbed the Countess confessed her crime to the Queen, who was so infuriated that she shook her, saying “God may forgive you, but I cannot.” The onyx is the emblem of conjugal felicity and by some is made the “birth stone” of the month of July. It is one of the stones prescribed for the ephod of the Jewish High Priest. The sardonyx was supposed by the ancients to be a different stone from the onyx. To it was ascribed the property of conferring eloquence upon its wearer. It is mentioned in Revelations as one of the stones forming the foundations of the Holy City. Onyx and sardonyx which come from the Orient are esteemed of much higher value in trade at the present time than those prepared in Germany. There seems to be no good reason for this, however, as the latter can be so skillfully made that it is impossible to distinguish them from the Oriental stones.