ji8 A SYSTEM OF 
5. By fcorification with lead, there has 
been extracted two ounces of filler 
out of a hundred pounds weight of 
the ftone. 
0 . 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 foiution, made either 
of crude, or of a perfedly 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 (i, 2.), and by the 
colour of the flag or glafs (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 ftones of the fili- 
ceous kind in general ; becaufe the 
purefl: and fineft blue lapis lazuli may 
be rubbed with the fteel to a white 
powder, although it takes a polifh 
like marble. 
9 The lapis lazuli, when perfeclly cal- 
cined, is a little attracted by the load- 
fione •, and fcorified with lead, the flag 
becomes of a greenifh colour, not 
fuch a colour as copper gives, but 
fuch as is always produced by iron 
mixed v/ith a calcareous fubfcance 
* I'he lap^s la7.uli is feldom found pure, but is moft ge- 
nerally f uii of veins of quartz, imieitonc, and marcafitc : how- 
ever. 
