212 Adams and Harrington — Alkali Hornblende and 



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 pow- 

 der now to consist of grains of hornblende and of garnet with 

 some composite grains consisting partly of nepheline. Fur- 

 ther separation became difficult since, as was subsequently 

 ascertained, the hornblende had a specific gravity of 3433, 

 and the specific gravity of the garnet was 3*739, while many 

 composite grains consisting of garnet and nepheline had a 

 specific gravity practically identical with that of the horn- 

 blende. 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 maintained at a temperature of from 200° to 240° 

 C. On allowing the mass to solidify, a portion of the powder 

 was found to have collected at the top of the mass, while the 

 rest was at the bottom, the intervening part being quite free 

 from mineral grains. The solid mass was then cut in two and 

 the salts dissolved by treatment with water. After three suc- 

 cessive separations the hornblende was obtained quite free 

 from grains of garnet — the only impurities present being some 

 composite grains consisting of garnet and nepheline. This 

 powder was then placed under a lens and all the composite 

 grains picked out by means of a fine needle. In this way a 

 quantity of pure hornblende sufficient for purposes of analysis 

 was obtained, while the garnet was obtained directly in a state 

 of purity without the necessity of a final separation by hand. 



Both minerals were found to be quite fresh and bright and 

 quite unacted upon by the fused salts. 



The. hornblendef was then analyzed by Dr. Harrington with 

 the following results : 



* " Ueber Scbwere Flussigkeiten zur Trennimg von Mineralien." Neues 

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



\ We would suggest Hastingsite as a varietal name for this hornblende, con- 

 necting it with the region where it occurs. 



