Augite from Vesuvius and Etna. 23 



1. Augite, Crater of Vesuvius, June, 1914, Wasliington analyst. 



2. Augite, Monte Somma. Doelter analyst. Tsehermak's Min. Petr. 



Mitth., 283, 1877. 



3. Augite, Vesuvius. Casoria, ref. Zs. Kryst., 42, 881, 1907. 



4. Pyi'oxenite, Monte Somma. Pisani analyst. Lacroix, C. E. 165, 209, 



1917. 



Earlier analyses. — The earlier analyses of Vesuvian 

 augites, collected by Dana, Hintze, and Doelter, and most 

 completely by Zambonini,^ are very unsatisfactory, either 

 because of their early dates, or because of their incom- 

 pleteness. However, two of them, which seem to be 

 somewhat less inferior than the others, are given in 

 Table I. While these older analyses show the general 

 characters of augite, yet they all are seriously defective in 

 that titanium dioxide and the alkalies are not determined 

 in any of them, although it is clear from my analysis, and 

 from our knowledge of augites elsewhere, that these 

 constituents are present in distinctly appreciable 

 amounts. The high alumina shown by them is due to the 

 presence of titanium dioxide. Furthermore, the iron 

 oxides are not separated in many of them. Lacroix has 

 called attention^ to these serious defects in all the existing 

 analyses of pyroxenes of Vesuvius, and I can only join 

 with him in urging the need for better analyses of this min- 

 eral group from Vesuvius and from other localities, and, 

 incidentally, call attention to the general inferiority of the 

 great majority of the analyses of pyroxenes, especially as 

 regards the fundamental points of selection of pure mate- 

 rial, and accuracy and completeness of the analyses. 



The publication of analyses of such inferior quality is 

 to be deplored, as leading possibly to seriously incorrect 

 generalizations at the hands of those who accept blindly 

 and without critical judgment any analysis that is offered 

 them. One of the striking features in the study of the 

 chemistry of minerals and rocks is the complacency with 

 Avhich such inferior work is accepted and published. Much 

 of it is based on impure material, often not ascertainedly 

 so, carried out by inexperienced analysts, by poor 

 methods, or with impure reagents ; and yet it is accepted 

 in good faith by both analyst and author. This state of 

 affairs has done much — much more than is generally 

 thought — to hinder the progress of our knowledge of the 

 chemistry of minerals. 



^ F. Zambonini, Mineralogia Vesuviana, 151, 1910. 

 «A. Lacroix, C. R., 165, 211, 1917. 



