48 MINERALS AND GEOLOGY OF CENTRAL CANADA. 



The rare metals cerium, uranium, &c., belong also to this group. 

 Reference should also be made to iron, nickel, cobalt and copper, as 

 the oxides of these metals, if in small quantity, might escape detection 

 by the reducing process. 



Group 2. Imparting no colour to the fluxes. Slowly dissolved by 

 borax, the glass remaining permanently clear : 



Alumina 



Moistened with nitrate of cobalt and then ignited, this base assumes 

 on cooling a fine blue color. 



Group 3. Imparting no colour to the fluxes. Rapidly dissolved 

 by borax, the glass becoming opaque on cooling or when flamed : 

 Magnesia. Lime. 



Moistened with nitrate of cobalt, and ignited, Magnesia becomes 

 pale-red in colour ; Lime, dark-grey. 



Group 4. Entirely dissolved by fusion with carb-soda. 



Baryta. Strontia. Lithia. Soda. Potash. 



Baryta compounds impart a distinct green colour to the point and 

 border of the flame. Strontia and Lithia colour the flame deep car- 

 mine-red. The crimson coloration is destroyed in the case of strontia 

 if the substance be fused with chloride of barium. Soda colours the 

 flame strongly yellow. Potash communicates to it a violet tint ; but 

 this colour is completely masked by the presence of soda, unless the 

 flame be examined through a deep blue glass.* 



* The presence of alkalies or alkaline earths (magnesia excepted) is most readily ascertained 

 in minerals by the use of a small pocket spectroscope. See the author's Blowpipe Practice. 



