462 DR T. THOMSON'S Analysis of some Minerals. 



country is called alumbre (alum), and applied to the same uses as 

 that salt. BOUSSINGAULT has analyzed a specimen from the same 

 locality as mine. He gives its constituents as follows : 



Sulphuric acid, . . . . 36.4 



Alumina, 16.0 



Water, ... . . . 46.6 



Oxide of iron, .... 0.4 



Lime, ....... 0.2 



Clay, 0.4 



100.0 



The colour of the specimen is white, here and there tinged 

 yellow, obviously from external impurities. 



In fine crystalline scales. 



Lustre silky. 



Taste that of alum, but stronger. 



Translucent. 



Very soft. 



Specific gravity 1 .6606. 



Before the blowpipe behaves like alum. 



Being subjected to a careful analysis, its constituents were 

 found as follows : 



Sulphuric acid, .... 35.872 



Alumina, 14.645 



Water, . . . . .... 46.375 



Peroxide of iron, .... 0.500 



Soda, ........ 2.262 



Mechanical impurity *, . . 0.100 



99.754 



* It was very ferruginous silica. 



