Optallio is called Oppalus also, and is a stone distinguished with colors of divers precious stones, as _Isid._ saith.... This stone breedeth onely in _Inde_ and is deemed to have as many virtues, as hiewes and colours. Of this _Optallius_ it is said in Lapidario, that this _Optallius_ keepeth and saveth his eyen that beareth it, cleere and sharp and without griefe, and dimmeth other men’s eyen that be about, with a maner clowde, and smiteth them with a maner blindnesse, that is called _Amentia_, so that they may not see neither take heede what is done before their eyen. Therefore it is said that it is the most sure patron of theeves. The opal seems to have appealed to Shakespeare as a fit emblem of inconstancy, for in “Twelfth Night” he makes the clown say to the Duke:[218] Now the melancholy God protect thee, and the Tailor make thy garment of changeable taffeta, for thy mind is very opal. That the beauty of the opal was fully appreciated in the sixteenth century is shown by the words of Cardano, who states that he once bought one of these stones for fifteen gold crowns and found as much pleasure in its possession as he did in that of a diamond that had cost him five hundred crowns.[219] Although superstitious beliefs were rather the rule than the exception in Cardano’s time, none of the silly fancies regarding the ominous quality of the opal were then current. It was reserved for the nineteenth century to develop these altogether unreasonable—and indeed almost inexplicable—superstitions. The ownership of so fair an object as a fine opal must certainly be a source of pleasure, and hence add to the good fortune of the owner. Although opal has been considered by some a stone of misfortune, black opal is regarded as an exceptionally lucky stone. Formerly black opals were artificially made by dipping the light-colored stone into ink, or by allowing burnt oil to enter cracks in the stone produced by heating. About the year 1900, however, a number of deposits of natural black opals were found in the White Cliff region of New South Wales, whence exceedingly beautiful gems have been secured, with wonderful flames of green, red, and blue in a black field. Some of these have sold for $1000 and even for a higher price, the smaller ones bringing from a few dollars upward each. It has been claimed that $2,000,000 worth have been sold from New South Wales. A remarkable example is figured on the frontispiece of this volume. The late F. Marion Crawford was a great admirer of this strangely beautiful variety of opal.