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Turcois, This was long thought to be 

 a natural Gem ; but it has fincc been dil- 

 covered to be only in reality the Bone of 

 an Animal, by Accident fallen into a Cop- 

 per Mine, whence it derives its flony and 

 mineral Qualities : It has not that fine 

 blue Colour when firft found, requiring 

 fome Art to bring it to Perfedlion, and 

 when done it does not for any Length of 

 Time continue, but becomes gradually 

 green j which is the Reafon of its not 

 being fo valuable as it would otherwife 

 be : Whilft it holds its Colour it is indeed 

 moft beautiful. 



Oculus Mundi is of a pale and uniform 

 Colour, a whitifh grey, no ways varied ^ 

 it is almoft entirely opake, and does not 

 take a good Poliih : When put into Wa- 

 ter for a fmall Space of Time, it becomes 

 confiderably tranfparent, and takes the 

 Colour of the yellow Cornelian, or rather 

 Amber, that is, a very fine bright pale 

 yellow j but it retains this Beauty only 

 whilft in the Water, taking, when dry, 



its 



