PETROGRAPHY OF THE KEWEENAW AN 



655 



analyses are new occurrences. As datolite is new to the state except 

 in the drift, it is worthy of' record that it has another occurrence, on 

 Crooked Creek. Record of metalhc copper from many points might 

 be made, but the mineral needs no analysis, except for silver, which 

 was not found. 



The Chemical Classification.^ — Grouping the twelve new 

 analyses of rocks that show little alteration (less than 3 per cent com- 

 bined water) with five earlier results which seem to be good, the 

 chemical character of the diabases may be summarized. More 

 results fall in the subrang Hessose, than any other, and this is a 

 persodic, docalcic, perfelic dosalane. The similar groups Bandose 



TABLE VIII 

 Analyses of Basic Diabase Dikes of Minnesota 



1. Diabase dike, Stearns Co., Minn, B. F. Noehl, student analyst. 



2. Olivine diabase dike, Carlton Co., Minn. W. H. Truesdell, student analyst. 



3. Diabase dike, Stearns Co., Minn. Average of two analyses, side and center of 

 14-foot dike, essentially the same. F. F. Grout, analyst. 



4. Diabase with phenocrysts of quartz and feldspar in a 5-foot dike. F. F. 

 Grout, analyst. 



Journal of Geology, X, 555. 



