About the middle of the eighteenth century, a peasant found a brilliant precious stone in some old ruins at Alexandria, Egypt. This stone was set in a ring. It was as large as a hazel-nut and is said to have been an opal cut _en cabochon_. According to the report, it was eventually taken to Constantinople, where it was estimated to be worth “several thousand ducats.”[214] The description given of this gem, its apparent antiquity, and the high value set upon it have contributed to induce many to conjecture that it was the celebrated “opal of Nonius.” Of course this was nothing but a romantic fancy. It is also quite certain that an opal would scarcely hold its play of color or compactness for twenty centuries, for most opals lose their water—slowly perhaps, but surely—within a lesser space of time. Even the finest Hungarian opals show some loss of life and color within a century or even less, and some transparent Mexican opals lose their color and are filled with flaws within a few years’ time. The Edda tells of a sacred stone called the yarkastein, which the clever smith Volöndr (the Scandinavian Vulcan) formed from the eyes of children. Grimm conjectures that this name designates a round, milk-white opal. Certainly the opal was often called _ophthalmios_, or eyestone, in the Middle Ages, and it was a common idea that the image of a boy or girl could be seen in the pupil of the eye. [Illustration: THE “ORPHANUS JEWEL” IN THE GERMAN IMPERIAL CROWN. From the “Hortus Sanitatis” of Johannis de Cuba [Strassburg, Jean Pryss, ca. 1483]; De lapidibus, cap. xcii. Author’s library.] Albertus Magnus describes under the name _orphanus_ a stone which was set in the imperial crown of the Holy Roman Empire. This gem is believed to have been a splendid opal, and Albertus describes it as follows: The orphanus is a stone which is in the crown of the Roman Emperor, and none like it has ever been seen; for this very reason it is called orphanus. It is of a subtle vinous tinge, and its hue is as though pure white snow flashed and sparkled with the color of bright, ruddy wine, and was overcome by this radiance. It is a translucent stone, and there is a tradition that formerly it shone in the night-time; but now, in our age, it does not sparkle in the dark. It is said to guard the regal honor.[215] Evidently this imperial gem was regarded as _sui generis_, for Albertus has just described the _ophthalmus lapis_, a name frequently bestowed upon the opal in medieval times, reciting the virtues usually ascribed to the opal for the cure of diseases of the eye, and the magic power of the stone to render its wearer invisible, wherefore it was denominated _patronus furum_, or “patron of thieves.”