A SYSTEM OF 



SECT. LV. 



i. The Opal. Opalus Paderota. 



It is the moll beautiful of all the flint 

 kind, owing to the changeable appearance 

 of its colours by reflection and refraction, 

 and mult therefore be defcribed under both 

 thefe circumftances. 



a. The Opal of Nonnius* the Sangenon of 

 the Indians. 



This appears olive-coloured by reflec- 

 tion, and feems then to be opaque, but 

 when held againfl the light, is found 

 tranfparent, , and of a fine ruby red. 



That opal is fuppofed to have been of 

 this kind, which Pliny mentions in his 

 Natural Hiftory, chap. 307. feet, xxi and 

 which he fays, was in the fenator No- 

 nius's porTeflion, who rather fuffered ba- 

 nifhment, than part with it to Antony. 



This Hone was in Rome at that time 

 valued at 20000 fefterces. But the ftone 

 here particularly defcribed, was found in 

 the ruins of Alexandria; it is about the 

 fize of a hazle-nut, and was bought for 

 a trifle of a French druggift, named 

 Roboly, and prefented to the French ge- 

 neral conful Lironcburt, who afterwards 

 offered it to fale in feveral places, for the 

 fum of 40,000 rixdollars. See Haffel- 

 quifl's Travels to the Eaft, under the ar- 

 ticle of Opal. * 



* This very ftone was in the year 1763 in the pofleffion 

 of his excellency the duke de Nivernois, then ambaffador to 

 the Britifh court, and I have often been honoured by his ex- 

 cellency of having it for fome days in my poiTelfion. D. C. 



There 



