ix8 A SYSTEM OF 



5. By rectification with lead, there has 

 been extracted two ounces of Giver 

 out of a hundred pounds weight of 

 the ftone. 



6. The prefence of filver is not difco- 

 vered with the fame certainty by the 

 fpirit of nitre as by the oil of vi- 

 triol. 



7. When the fpirit of fal ammoniac is 

 added to any folution, made either 

 of crude, or of a perfectly calcined 

 lapis lazuli, there is no blue colour 

 produced ; which proves that this co- 

 lour is not owing to copper, as fome 

 have pretended : and this is farther 

 confirmed by the fixity of the blue 

 colour in the fire (1, 2.), and by the 

 colour of the flag or glais (2.). 



8. It is a little harder than the other 

 kinds of zeolites, but does not how- 

 ever in hardnefs approach to the 



\ quartz, or to other {tones of the fili- 



ceous kind in general ; becaufe the 

 pureil and fmeft blue lapis lazuli may 

 be rubbed with the fleel to a white 

 powder, although it tak^s a polifh 

 like marble. 

 9 The lapis lazuli, when perfectly cal- 

 cined, is a little attracted by the load- 

 ftone; arid fcorified with lead, the flag 

 becomes of a greenifn colour, not 

 fuch a colour as copper gives, but 

 fuch as is always produced by iron 

 mixed with a calcareous fubftance *. 



* The lapis lazuli is feldom found pure, but is mod ge- 

 nerally full of vein* of quart?,, liiueftone, and marcafite : how- 

 ever, 



