36 Clarice and Steiger — Action of Ammonium Chloride. 



Aegirite. 



Material from the well known locality at Magnet Cove* 

 Arkansas. Not absolutely pure, but somewhat contaminated 

 by ferric hydroxide. This impurity is evident in a discussion 

 of the ratios furnished by the analysis, but is not serious. It 

 does not affect the problems under consideration. By heating 

 with ammonium chloride the mineral was only slightly changed. 

 In the leach water from the product there were 1 # 66 per cent 

 (AlFe) 2 3 , 0*51 CaO, and 1-18 Na 2 0. Analyses as follows : 

 A of the aegirite, B of the air dried, leached residue. 



A B 



Si0 2 50-45 51-83 



MO. 2-76 ) 



Fe 2 3 23-42 f lb ^ 



FeO _. 5-26 5*69 



MnO -10 



MgO 1*48 1-58 



CaO 5-92 5-74 



NaO 9-84 



KO _-.... -24 



9-0 



NH, _.._ .... -26 



H 2 Oatl00° -15 ) 



H 2 above 100° '40 [ JU 



100-02 100-31 



Of the silica in the residue 4*42 per cent was soluble in 

 sodium carbonate solution. Anr ammonium derivative was not 

 formed. 



From these data we see that the three iron silicates are very 

 differently attacked by ammonium chloride ; ilvaite very 

 strongly, riebeckite moderately, and aegirite but feebly. The 

 aegirite is the most stable, and at the same time the commonest 

 of the three. A comparison of the aegirite analysis with that 

 made by J. Lawrence Smith of material from the same region, 

 shows notable differences. The mineral evidently varies in 

 composition ; the variation depending upon the relative 

 amounts of the two silicate molecules Fe]N"aSi 2 6 and R // Si0 3 . 

 Two samples taken from different parts of the same rock area 

 are not necessarily identical in composition. 



Serpentine. 



In 1890 Clarke and Schneider published an investigation* 

 relative to the action of gaseous hydrochloric acid upon vari- 

 ous minerals. Among these were the three species serpentine,, 



* Bulletin 78, U. S. Geol. Survey, p. 11. 



