J. E. Whitfield — Natural Borates and Borosilicates. 285 



B 2 3 12-04 



Fe 2 3 31-93 



Feb.. 15-78 



MgO 30-57 



MnO 0-16 



HO 3-62 



100-10 



The ratios are B 2 3 : Fe 2 3 : FeO : MgO : H 2 0-17 : 24 : 24 : 76 : 

 20; taking all the protoxides together with the water as basic, 

 we have B 2 3 : Fe 2 3 : BO-3 : 4 : 20. G. Tschermak* obtained 

 for boric acid, by Marignac's and by Stromeyer's method, 16*09 

 per cent and 15-06 per cent respectively, but gives no water, 

 and from his results deduces the formula 3MgO . B 2 O s +FeO. 

 Fe 2 O s . If he sought for water by ignition, the oxidation of 

 ferrous iron might easily have led to error. 



Datolite. — The material investigated was the well known 

 mineral from Bergen Hill, N. J., and consisted of crystals about 

 gmm j n (Ji am eter, translucent, white or of a pale greenish color. 

 I have been unable to find any published analysis of the min- 

 eral from this locality, although it has been known for so long 

 a time. By analysis I obtained: 



Si0 2 35-U 



FeO -31 



CaO 35-14 



B„0 3 22-60 



HO 6-14 



99-93 



The small amount of iron is undoubtedly present as an impu- 

 rity ; leaving this out, the molecular ratios are Si0 2 : CaO : B 2 3 : 

 H 2 O-60 :63:32:34, giving the formula B 2 3 . H„0 . 2CaO . 

 2Si0 2 , or H . CaSi0 3 . B0 2 . 



Danburite, from Bussell, St. Lawrence Co., 1ST. Y. — This 

 mineral has been fully described by Professors Brush and 

 Dana,f although from the description given by them of the 

 color of their specimen, I imagine they had material differing 

 somewhat from mine. The mineral analyzed was reddish yel- 

 low to pink in color, brilliant in luster and associated with 

 pyroxene, quartz and calcite. In the analysis referred to^: the 

 boric acid was determined by Stromeyer's method. The fig- 

 ures obtained by my analysis are given in the first column, the 

 second is the analysis made by Mr. W. J. Comstock for Pro- 

 fessor Brush. 



*Tsch. Min. Mitth., 1874, p. 59. f Amer. Jour. Sci., Ill, xx, 111, 1880. 



\ Loc. cit. 



