THE VOLCANOES AND ROCKS OF PANTELLERIA 



19 



general run of camptonose magmas. The iron oxides, lime, the 

 alkalies, and manganese are about normal, while phosphorus 

 is decidedly high. 



The norms show some interesting features. The entire absence 

 of anorthite, except in the most salic and most femic extremes, and 

 the poverty in diopside, except in the basalts, are striking, as well 

 as the abundance of excess silica (normative quartz) in all except 

 the trachytes and basalts. Still more striking are the abundance 

 of acmite and the prevalence of sodium metasilicate along with it 

 in all except the extremes just mentioned, and the large amounts 

 of ilmenite. 



Foerstner^s analyses. — It is always an unpleasant task to criti- 

 cize adversely the work of another, but in the present case such a 

 course seems to be unavoidable, as Foerstner's analyses, especially 

 of the pantellerites, have been widely quoted and accepted as 

 accurate, being the only ones heretofore available for these rocks. 

 The numerous new analyses, most carefully made according to 

 modern methods, indicate that those given by Foerstner are incor- 

 rect and incomplete in certain important particulars, and that 

 many of them are subject to errors, apparently systematic in 

 character. The comparison is shown in the accompanying table, 



TABLE III 



Comparison of Old and New Analyses 



1,2. Trachyte 



3, 4. Aegirite pantellerite 



S, 6, 7. Hyalopantellerite 

 8, 9, 10. Basalt 



