Q PROCEEDINGS OF THE NATIONAL. MUSEUM vol. 6ff 



One of these end members is evidently composed of RaOrRO:- 

 R2O3 : SiOg in the ratios 1 : 2 : 2 : 10 and the variation in composition 

 was toward a second end member where RjC) : RO : R2O3 : SiOo= 

 1 : 1 : 3 : 10. All the analyses of glauconite given in Table II and 

 also the analyses that were rejected for various reasons lie between 

 these two end members, but there is a possibility of a wider range of 

 composition as the chemical relationships permit variation between 

 1:3:1:10 and 1:0:4:10. 



The ratio of K^O to SiOg is approximately 1 to 10 as the average 

 for all analyses used is 1 to 9.7. 



The chemical composition of the ideal end members as just ob- 

 tained and the analyses of glauconite have been graphically plotted 

 on two coordinates in Figure 1. The elements that isomorphously 

 replace one another have been combined as previously described 

 and recalculated to 100 per cent so that only K2O, MgO, FeoOg, SiOz, 

 and H2O are considered. Water was included in the calculations 

 but was not plotted as its line is very close to that of MgO and thus 

 involved an overlapping of points. 



The black dots in Figure 1 represent end members and the 

 circles represent analyses. The vertical coordinate on the diagram 

 shows the chemical composition in per cent, and the horizontal co- 

 ordinate the proportion of the two end members. Thus the chemical 

 composition of a glauconite is represented graphically by four circles 

 lying on a single vertical line, the upper one being SiOg, the next 

 R2O3 recalculated as FcaOg, the next R2O recalculated as K2O, and 

 the lowest RO recalculated as MgO. The departure from the 

 theoretical composition is shown by the distance of the circles from 

 the curve, and where the analyses exactly conform to theory the 

 circles fall directly upon the curve. With few exceptions the circles 

 fall very close to this ideal line and the analyses thus plotted repre- 

 sent so consistent a series that it seems evident that the end mem- 

 bers have been correctly deduced. It will be seen that MgO de- 

 creases as Fe203 increases; that SiOg decreases in per cent, but not 

 in ratio as Fe203 increases; and that the ratio of KgO to SiOg is 

 constant. 



The same relationships are shown numerically in Table 11. The 

 three component diagram was used to determine the proportion of 

 the two end members represented in each glauconite analysis. An 

 ideal composition based on this deduced proportion was then calcu- 

 lated for each analysis given in the table, and the column immediately 

 following the analysis gives the ratio of this ideal composition to 

 the actual composition. Thus 100 represents exact agreement of an 

 element in the analysis with the assumed proportion, and a depar- 

 ture from 100 shows a failure of the element to conform to the ideal 

 composition. If an analysis conformed exactly to theory, 100 would 



