﻿80 Canadian Record of Science. 



In order to determine the chemical composition of this 

 somewhat remarkable variety of hornblende from the 

 Dungannon rock, it was decided to separate a portion for 

 analysis. A considerable quantity of the rock was 

 accordingly reduced to powder and passed through a sieve 

 of 43 meshes to the inch — the rock being rather coarse in 

 grain — and after having been freed from dust was treated 

 with Thoulet's solution, having a specific gravity of 3-13, 

 in a large separating funnel. In this way an almost 

 complete separation of the colored constituents was 

 effected. These latter, which sank in Thoulet's solution,, 

 were subjected to the action of a bar magnet and then 

 treated with 'dilute hydrochloric acid, and various 

 impurities thus removed. The purified powder was then 

 treated first with Klein's solution, having a specific 

 gravity of 3-22, and then with methylene iodide, having a 

 specific gravity of 3*323. In both fluids practically 

 everything sank, only a few composite grains floating. 

 A microscopic examination showed the powder now 

 to consist of grains of hornblende and of garnet with some 

 composite grains consisting partly of nepheline. Further 

 separation became difficult since, as was subsequently 

 ascertained, the hornblende had a specific gravity of 

 3*433, and the specific gravity of the garnet was 3739, 

 while many composite grains consisting of garnet and 

 nepheline had a specific gravity practically identical with 

 that of the hornblende. As the electro-magnet was found 

 to be useless, both minerals being readily attracted by it^ 

 Retger's silver nitrate method was employed.^ The silver 

 nitrate was fused in a properly arranged test tube, and 

 after the introduction of the powder, potassium nitrate in 

 powder was gradually added to the fused mass until the 

 garnet fell, the whole being frequently stirred and main- 

 tained at a temperature of from 200° to 240° C. On 



1 " Ueber Schweie Flussigkeitken zur Trenming von Mineialien." Neues Jahrbuch 

 fur Mineralogie, etc., 1889, ii, p. 190. 



