s H. S. Washington — -New Leucite Rock. 45 



As some of the melilite crystals in the crevices were 

 included in the material analysed, the mode given in the 

 first column is too high in melilite, and a presumably 

 more correct one is given by the figures in parentheses. 



For the chemical analysis a thick slice was made 

 through the center of the specimen, and the melilite crys- 

 tals in the cavities, and the lining of these, were removed 

 so far as possible, though they could not be wholly 

 avoided without unduly reducing the quantity of mate- 

 rial. The analysis furnished the following results : 



SiO, 45-49 ILO-f 0-93 



Al.,63 17-66 H,0— 005 



Fe,0 3 0-81 TiO, 0-13 



Feb 1-45 Po0 5 016 



MgO 4-27 S0 3 none 



CaO 16-72 CI 003 



Na 2 1-66 MnO trace 



K,0 11-44 



100-80 



This analysis is remarkable in its high potash and 

 lime. Both the silica and alumina are distinctly lower 

 than in italite, the oxides of iron are about the same in 

 their total amount, though in inverse proportions, mag- 

 nesia is decidedly higher, while the percentage of soda 

 in both is identical. Two features of interest among the 

 minor constituents are the figures for Ti0 2 and S0 3 . 

 The higher titanium in the italite is evidently connected 

 with the presence of the titaniferous andradite, which is 

 wanting in the other rock. In this latter not a trace of 

 S0 3 could be detected, and but little more than a trace 

 of CI, showing the absence of minerals of the sodalite 

 group. 



The norm of the rock is calculated to be : 



Anorthite 6-95 Olivine 8-81 



Leucite 47-70 Calcium orthosilicate . 23.22 



Nephelite 7-67 Magnetite 1-16 



Kaliophilite 3-95 Ilmenite 0.30 



Apatite 0-34 



It is clear that most of the normative anorthite and 

 olivine go into modal augite ; a small amount of each, 

 with a little of the nephelite, going into the melilite. As 

 melilite has a ratio of bases to silica slightly greater than 

 2 : 1, the orthosilicate ratio, some silica will be thus lib- 



