OPALUS.	271
	Pliny justly observes (xxxvii. 21), "the Opal differs at once very much and very little from the Beryl," referring, it would appear, to the glassy texture of its substance, yet with the grand distinction of its iridescence. It came next to the Emerald in value : and naturally so, being almost the only one of the really precious stones of which the full perfection could be developed, by the simple process of polishing known to the Romans. For this stone is only cut en cabochon ; and owing to its extreme softness, the polishing is a matter of time and care alone. This is the sole instance where Pliny has quoted the selling price of a precious stone : the famous Opal of Nonius, then still in existence, as large as a hazel-nut (the greatest magnitude then attained by the stone), valued at 20,000/. of our money (vicies H. S.). Nonius was proscribed by M. Antony for the sake of this gem ; but made his escape, carrying off the ring along with him, the sole relic of his fortune : putting up with exile rather than make his peace with the Triumvir by the surrender of the coveted treasure. The finest Opal of modern times was the Empress Josephine's, entitled the " Burning of Troy," from the innumerable red flames blazing upon its surface, the reverse being perfectly opaque. The present owner of this unique gem is unknown. The Turks of our day esteem the Opal as highly as the Diamond, and readily give 1000l. for one of the size just named. "India," says Pliny, "is the sole mother of the Opal." This region (or perhaps Arabia) continued the only source of the supply of the best stones till a recent period. When De Boot wrote there was but one mine known in Hungary, and that nearly filled up with rubbish ; and which besides, he remarks, had never furnished anything but the second quality of Opals, the first even then coming from India. Some mineralogists doubt the fact that any region of the East Indies produced the true Opal, merely because no such gem is now brought from thence ; but the same argument applies here as in the case of the true Emerald, not at this time found in that country, formerly the principal source of the stone. The Hungarian mines of Czerve-nitza (where this gem occurs embedded in porphyry), a region inaccessible to the Romans of Pliny's age. now supply the finest