122 Elements of Mineralogy* 



ftalized ; it is much harder than green fluors 

 or green quartz. 



When diftilled, a little of its Earth fub- 

 limes ; it lofes its tranfparency and colour in 

 fire, but does not melt per fe. 



Mr. Achard found 100 parts of it to con- 

 tain 95 of filiceous Earth, 1,7 of calcareous 

 Earth, 1,2 of magnefia, 0,4 of iron, and o ? (5 

 of copper. 



SPECIES IX. 



Siliceous Earth intimately mixed 'with blue mar- 

 tial Fluor ) and a Jmall Proportion of Gyp- 

 fum. 



Lapis Lazuli. 



The colour of this fione is a beautiful 

 opake blue, which varies a little in intenfity, 

 and is generally fprinkled over with yellow, 

 bright, pyritaceous fpecks or ftreaks : it oh- 

 ftinately retains its colour in a ftrong heat, 

 which diftinguifhes it from other blue ftones : 

 it is of an equable or very fine granular texture, 

 and takes a beautiful poliih : its fpecific gravity 

 is 3,054, 



If powdered and not calcined, it effer- 

 vefces very flightly with acids, but if cal- 

 cined^ 



