MINERALOGY. 51 



In confequence of the ignorance I plead in 

 regard to thefe forts of ftones, I have given 

 this a place by itfelf. 



Saphires are faid to be found in Alfatia, at 

 St. Amarin, but accounts of this kind are in 

 general not to be depended upon, as the 

 rluors are frequently met with in collec- 

 tions and the druggifls fhops under the 

 name of faphires, when they are of a deep 

 blue colour -, not to mention that the quartz 

 is always termed a precious (lone, whenever 

 it is found clear, and of a fine colour. The 

 faphire is faid to lofe its blue colour in the 

 fire. Thofe which are but a little tinged are 

 called white faphires. The faphire is feldom 

 found of a very deep blue colour, and free 

 from parallel flaws which run through it -j% 



SECT. XLV. 



C. Topaz. Topazius, gemma. 



This is a precious flone, which, when 

 rough and perfect, is fold in a criftalliied 



f The faphires in their rough or native ftate criftallize 

 moft generally like two oblong hexagonal pyramids pointed 

 at their tops, and joined at their bafes : yet they are fome- 

 times found of an hexagonal columnar form. In the fire they 

 lofe their blue colour. 



I have found fome of the deep blue faphires, and fome of 

 a milky colour, which, when looked through, varied their co- 

 lours in the fame manner as the milky or bluifh opals (Sect. iv. 

 2, 3.) : this is however no reafon why rhofe opals mould be 

 ranked under the name of faphire, and lefs fo, lince there 

 are aifo agars found of the fame quality (Seel. lx. in the note) 

 it might rather give rife to a quefiion, whether the name of 

 milky or bluifh opal is not to be confidered as a vague term, 

 iince that principal quality is found in ftones of a fomewhat 

 different nature, tho' they all belong to the flinty order ? E. 



E 2 form 



