64 Scientific Proceedings, Royal Dublin Society. 



The glucinurn, along with some of the iron, was separated from 

 the alumina by carbonate of ammonia, subsequently precipitated 

 by ammonia, and weighed as the oxide along with some iron, which 

 was then estimated volunietrically. 



This sample of mixed beryl and orthoclase may then be consi- 

 dered, with little doubt, as containing some 42 per cent, of the latter 

 mineral, and originally some 58 percent, of beryl. The percentage 

 composition of four other crystals, all showing well-marked hexa- 

 gonal faces, was also investigated by taking specific gravities. 



1. White homogeneous crystal, with beryl lustre. Very hard 

 all over surface. 



Weight, 24-803. Sp. gr., 2-69. 



3. Piebald crystal. Heterogeneous appearance. 



Weight, 20-554. Sp. gr., 2-59. 



Beryl, . . 39 

 Orthoclase, . 61. 



4. Same appearance as 3. 



Weight, 21-152. Sp. gr., 2.57. 



Beryl, . . 30 

 Orthoclase, . 70. 



These computations assume the specific gravity of beryl as 

 2-722 ; of orthoclase as 2*510. It is to be remembered that other 

 values are assignable, but that these seem fairly well borne out by 

 the analysis. 



