Washington — Kaersutite from Linosa and Greenland. 197 



acute bisectrix on the universal stage gave 2V= 81°. This 

 value can be considered only fairly accurate because of the 

 deep color of the mineral which tends strongly to veil the 

 optical phenomena, but it agrees satisfactorily with the calcu- 

 lated value, much better, indeed, than in the case of the 

 Linosa hornblende. 



Chemical Composition. — The chemical analysis was carried 

 out on about 2 grams of carefully selected fragments, which, 

 after crushing and washing free from dust, were treated with an 

 electro-magnet to remove the few particles which contained 

 ore grains. The microscope indicated that but few of these 

 were present as inclusions, and the very small amount thus 

 removed is in harmony with the observations. The only inclu- 

 sions of note are of apatite, the needles of which penetrate 

 the hornblende to a very considerable extent. As the mineral 

 power was somewhat acted on by acid it was thought best not 

 to remove these inclusions by its use, but to correct the analy- 

 sis for their presence by determining P 2 5 . Apart from these 

 apatite inclusions the material analyzed was extremely pure, 

 as is shown in fig. 4, in which the enhedral apatites are well 

 seen. It was dried at 110° prior to the analysis, which was 

 carried out by the methods adopted in the previous one. 



Lorenzen (p. 30) seems to have had great difficulty, using 

 Doelter's method, in decomposing the mineral with sulphuric 

 and hydrofluoric acids to determine FeO and Fe 2 3 . He 

 reports the value FeO = 6*61 per cent in one case, but pre- 

 fers to consider all the iron as ferrous in the statement of his 

 analysis. Using the simple Pratt method, I had no difficulty 

 in the solution of the finely powdered mineral in six minutes, 

 and the result given here" may be accepted as fully as correct 

 as in the case of the Linosa hornblende, though the amount on 

 hand did not permit of a duplicate determination. 



Special search was made for tin, as 0*26 per cent Sn0 2 was 

 reported by Lorenzen, but with absolutely negative results. 

 The method adopted was essentially that of Baley as outlined 

 by Classen.* The mineral powder was decomposed by evapo- 

 ration to dryness with nitric and hydrofluoric acids, which 

 would not lead to loss of tin by volatilization as tin fluoride is 

 decomposed by heating. The residue was dissolved in hot 

 dilute hydrochloric acid, filtered, and the filtrate treated with 

 pure zinc, which would precipitate any tin. Only a very 

 slight residue remained, which was wholly soluble in nitric 

 acid. ^Neither this solution nor the previous filtrate gave any 

 precipitate with H 2 S or other reaction for tin. We therefore 

 consider that our hornblende contains no tin, and that the 



* A. Classen, Ausgew. Method, Anal. Chem., i, 1901, p. 184. 



