ART. 2 PROPERTIES OF GLAUCONITE ROSS " 5 



heavy solution (potassium iodide and mercury iodide) was used in 

 the separation of the glauconite, and since this mineral exchanges 

 bases so readily that it can be used as a water softener, it is probable 

 that the original potassium content was considerably augmented. 

 On account of the possible error in potash content all of Glinka's 

 analysis have been rejected, though some of them may undoubtedly 

 be good. 



Glauconite of undoubted purity contains very little calcium, and 

 in fact there is commonly only enough calcium to combine with 

 phosphorus when carbonates are completely absent. Silica is always 

 low where calcium is high, and it is evident that calcium is present 

 as an impurity, probably as calcite and possibly as gypsum in some 

 specimens. For this reason all analyses that contained 1 per cent 

 or more of calcium oxide (CaO) have been rejected and the cal- 

 cium in the analyses used has not been included among the essential 

 bases in the derivation of the chemical formula. 



The analyses of glauconite that have been made on the best mate- 

 rial usually contain only small proportions of sodium, but it has 

 been suggested^ that there may be a sodium form of glauconite. 

 This the writer is unable to confirm or disprove, but 3 analyses 

 containing over 1 per cent of sodium oxide (NaoO) have been in- 

 cluded in the tables. 



The modern glauconites dredged from the sea bottom are fine- 

 grained and earthy and so their purification for analysis has been 

 very difficult. The analyses of three such specimens have been 

 deemed good enough to be used in the chemical interpretation of 

 glauconite, but most of those given in the literature were obviously 

 made on very impure material. In Table II are listed 17 analyses 

 that appear to be good enough to be used in an interpretation of 

 the chemical composition of glauconite. 



As a first step in interpreting these analyses ALOg was combined 

 with Fe^Og, FeO with MgO, Na^O with K^O, H^O was left out of 

 consideration for the time being, and small amounts of P2O5, CaO, 

 etc., were disregarded as they no doubt form impurities. The com- 

 position was then recalculated to 100 per cent and FCgOg, MgO, 

 and KoO plotted on a three component diagram (not reproduced 

 here). The ratio between KoO and SiOs is constant and so the rela- 

 tions were not obscured by neglecting SiOg for the time being and 

 thus the failure to plot four interdependent variables. The dots rep- 

 resenting composition fell along a fairly straight line and it was evi- 

 dent that glauconite contains only two components or end members. 

 The analyses that were inferior were also plotted and proved to be 

 fairly close to the line of ideal composition and even those that 

 were very poor indicated no systematic variation from the ideal. 



« Hallimond, A. P., Mineralogical Magazine, vol. 19, No. 98, pp. 332-333. 1922. 



