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Hyacinthus, Sapphire, Corundum

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HYACINTHUS.
work in relief in the same material, the well-known design of Hebe feeding the Eagle ; the stone, heartshaped and of fine colour, 1-1/2 x 1-1/4 inches in dimension. The work, apparently belonging to the times of Hadrian, is of considerable merit, though producing but little effect, from the clouded surface of the gem upon which such admirable skill and patience have been lavished, a circumstance of itself attesting the date of its execution. The stone has a hole drilled through its longer axis, evidently done in India, that it might be worn as a bead, before it was purchased by the Roman lapidary, to be engraved as a cameo; for the work in one place has cut down into this perfo­ration.
Of modern works, the finest ever done is the portrait of Pope Paul III., ascribed, no doubt with justice, to the famous Ales-sandro Cesati, in the Pulsky Collection. It is a beautiful Sap­phire 3/4 inch square, a truly inestimable gem, both for its fine quality and the spirit and life of the engraving, and was cer­tainly the signet of the Pontiff himself. Inferior to this in point of art was the bust of Henri IV. by Caldoré (with his initials) on a large octagonal stone of pale colour, but possessing great his­torical interest. A large number of pale Sapphires may be seen in cabinets, engraved with heads or figures, usually but poorly done, in the stylo of the Cinque-cento. The reason is explained by De Laet (i. 7) :—" The sort which is pale, or watery, is painted on the back with indigo, so as to imitate the sky-blue and superior kind, although this method is forbidden to jewellers to employ unless there be something engraved upon the stone, in order that its quality may be distinguished."
The pale Sapphires can be rendered entirely colourless by exposure for some hours to a regulated heat, and thereby acquire great brilliancy, so as often to be passed off as real Diamonds. But there is one infallible distinction between this uncoloured gem, and also between the White Topaz, and the true Diamond, that neither possesses the iridescence always displayed by the latter when catching the light at a certain angle.4
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