<t 10 Elements of Mineralogy. 



and there called a felt-fpar, I extrafted 72 per 

 cent, of filex, 22 of argill, and about 6 of 

 mild calcareous Earth, but could not melt it 

 by the blow-pipe. I believe the calcareous 

 Earth was not in a mild ftate in the ftone. 

 It fhewed no fign of iron notwithftanding its 

 flight reddilh colour, nor of any other 

 metal. 



SPECIES IV. 



Siliceous Earth intimately mixed with about { 

 of its weight of Argill^ and 1. or ^ of its 

 weight of Calx of Iron. 



Jafper^ Diaffro of the Italians. 



This fpecies alfo borders on the former,, 

 but it has a ftill duller, lefs glaffy, and more 

 earthy appearance in its fracture, and its gra- 

 nular texture is more diftincl:; it alfo often 

 breaks with conchoidal furfaces ; it is capable 

 of a fine polifh ; its colour is generally red- 

 difh or green, or ftriped ; but it is alfo found 

 blue, grey, or whitifh ; its fpecific gravity is 

 from 2,68 to 2,778, or more, when it con- 

 tains more iron. In fire it; retains its colour 

 much longer than petro filex, never decrepi- 

 tates, but grows rather harder, as Mr. Wedge- 

 wood affured me, and does not melt per fe in 

 clay crucibles, though it does in thofe made 

 of chalk. Alkalis borax and microcotmic 



fait 



